SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                  SCHEDULE 13D

                    Under the Securities Exchange Act of 1934
                               (Amendment No. 3)*


                                  MASTEC, INC.
                                  ------------
                                (Name of Issuer)

                     COMMON STOCK, PAR VALUE $.10 PER SHARE
                     --------------------------------------
                         (Title of Class of Securities)

                                    576323109
                                  ------------
                                 (Cusip Number)

                                  Jose Sariego
                     Senior Vice President - General Counsel
                                  MasTec, Inc.
                              3155 N.W. 77th Avenue
                              Miami, Florida 33122
                                 (305) 599-1800
                -------------------------------------------------
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)


                                  MARCH 1, 2000
                      ------------------------------------
                      (Date of Event which Requires Filing
                               of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition that is the subject of this Schedule 13D, and is filing this
schedule because of ss.ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box [ ].

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                        (Continued on following page(s))

                                     Page 1


<PAGE>

<TABLE>
<CAPTION>
-------------------------------------------                                     -------------------------------------------
CUSIP NO. 576323109                                         13D                   PAGE 2
-------------------------------------------                                     -------------------------------------------

-------- ---------------------------------------------------------------------  -------------------------------------------
<S>       <C>                                                                                                       <C>
1         NAME OF REPORTING PERSON
          S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          JORGE MAS
-------- ------------------------------------------------------------------------------------------------------------------
2         Check the appropriate Box if a Member of a Group                                                          (a) [_]
                                                                                                                    (b) [X]
-------- ------------------------------------------------------------------------------------------------------------------
3         SEC USE ONLY

-------- ------------------------------------------------------------------------------------------------------------------
4         SOURCE OF FUNDS*

          OO
-------- ------------------------------------------------------------------------------------------------------------------
5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEMS 2(d) or 2(e)                                                                                            [_]
-------- ------------------------------------------------------------------------------------------------------------------
6         CITIZENSHIP OR PLACE OF ORGANIZATION

          USA
-------- ------------------------ -----------------------------------------------------------------------------------------
NUMBER OF                    7        SOLE VOTING POWER
SHARES                                    13,416,545
BENEFI-                   ------- -----------------------------------------------------------------------------------------
CIALLY                       8        SHARED VOTING POWER
OWNED BY                                  0
EACH                      ------- -----------------------------------------------------------------------------------------
REPORTING                    9        SOLE DISPOSITIVE POWER
PERSON                                    13,416,545
WITH                      ------- -----------------------------------------------------------------------------------------
                            10        SHARED DISPOSITIVE POWER
                                          0
-------- ------------------------ -----------------------------------------------------------------------------------------
11        AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          13,416,545
-------- ------------------------ -----------------------------------------------------------------------------------------
12        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
          SHARES*                                                                                                       [_]
-------- ------------------------ -----------------------------------------------------------------------------------------
13        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          43.2%
-------- ------------------------ -----------------------------------------------------------------------------------------
14        TYPE OF REPORTING PERSON

          IN
-------- ------------------------ -----------------------------------------------------------------------------------------
</TABLE>



<PAGE>

<TABLE>
<CAPTION>
-------------------------------------------                                     -------------------------------------------
CUSIP NO. 576323109                                         13D                   PAGE 3
-------------------------------------------                                     -------------------------------------------

-------- ---------------------------------------------------------------------  -------------------------------------------
<S>       <C>                                                                                                       <C>
1         NAME OF REPORTING PERSON
          S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          JORGE L. MAS CANOSA HOLDINGS I LIMITED PARTNERSHIP
-------- ------------------------------------------------------------------------------------------------------------------
2         Check the appropriate Box if a Member of a Group                                                          (a) [_]
                                                                                                                    (b) [X]
-------- ------------------------------------------------------------------------------------------------------------------
3         SEC USE ONLY

-------- ------------------------------------------------------------------------------------------------------------------
4         SOURCE OF FUNDS*

          OO
-------- ------------------------------------------------------------------------------------------------------------------
5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEMS 2(d) or 2(e)                                                                                            [_]
-------- ------------------------------------------------------------------------------------------------------------------
6         CITIZENSHIP OR PLACE OF ORGANIZATION

          TEXAS
-------- ------------------------ -----------------------------------------------------------------------------------------
NUMBER OF                    7        SOLE VOTING POWER
SHARES                                    7,515,811
BENEFI-                   ------- -----------------------------------------------------------------------------------------
CIALLY                       8        SHARED VOTING POWER
OWNED BY                                  0
EACH                      ------- -----------------------------------------------------------------------------------------
REPORTING                    9        SOLE DISPOSITIVE POWER
PERSON                                    7,515,811
WITH                      ------- -----------------------------------------------------------------------------------------
                            10        SHARED DISPOSITIVE POWER
                                          0
-------- ------------------------ -----------------------------------------------------------------------------------------
11        AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          7,515,811
-------- ------------------------ -----------------------------------------------------------------------------------------
12        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
          SHARES*                                                                                                       [_]
-------- ------------------------ -----------------------------------------------------------------------------------------
13        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          24.2%
-------- ------------------------ -----------------------------------------------------------------------------------------
14        TYPE OF REPORTING PERSON

          PN
-------- ------------------------ -----------------------------------------------------------------------------------------
</TABLE>



<PAGE>

<TABLE>
<CAPTION>
-------------------------------------------                                     -------------------------------------------
CUSIP NO. 576323109                                         13D                   PAGE 4
-------------------------------------------                                     -------------------------------------------

-------- ---------------------------------------------------------------------  -------------------------------------------
<S>       <C>                                                                                                       <C>
1         NAME OF REPORTING PERSON
          S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

          JORGE MAS HOLDINGS I LIMITED PARTNERSHIP
-------- ------------------------------------------------------------------------------------------------------------------
2         Check the appropriate Box if a Member of a Group                                                          (a) [_]
                                                                                                                    (b) [X]
-------- ------------------------------------------------------------------------------------------------------------------
3         SEC USE ONLY

-------- ------------------------------------------------------------------------------------------------------------------
4         SOURCE OF FUNDS*

          OO
-------- ------------------------------------------------------------------------------------------------------------------
5         CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEMS 2(d) or 2(e)                                                                                            [_]
-------- ------------------------------------------------------------------------------------------------------------------
6         CITIZENSHIP OR PLACE OF ORGANIZATION

          TEXAS
-------- ------------------------ -----------------------------------------------------------------------------------------
NUMBER OF                    7        SOLE VOTING POWER
SHARES                                    5,587,311
BENEFI-                   ------- -----------------------------------------------------------------------------------------
CIALLY                       8        SHARED VOTING POWER
OWNED BY                                  0
EACH                      ------- -----------------------------------------------------------------------------------------
REPORTING                    9        SOLE DISPOSITIVE POWER
PERSON                                    5,587,311
WITH                      ------- -----------------------------------------------------------------------------------------
                            10        SHARED DISPOSITIVE POWER
                                          0
-------- ------------------------ -----------------------------------------------------------------------------------------
11        AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          5,587,311
-------- ------------------------ -----------------------------------------------------------------------------------------
12        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN
          SHARES*                                                                                                       [_]
-------- ------------------------ -----------------------------------------------------------------------------------------
13        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          18.0%
-------- ------------------------ -----------------------------------------------------------------------------------------
14        TYPE OF REPORTING PERSON

          PN
-------- ------------------------ -----------------------------------------------------------------------------------------
</TABLE>



<PAGE>

                         AMENDMENT NO. 3 TO SCHEDULE 13D

         This Amendment No. 3 to Schedule 13D is filed jointly on behalf of
Jorge L. Mas Canosa Holdings I Limited Partnership (the "Family Partnership"),
Jorge Mas Holdings I Limited Partnership ("Jorge Mas Holdings"), and Jorge Mas
(collectively, the "Reporting Persons"). This Amendment No. 3 to Schedule 13D
amends and updates the statements on Schedule 13D previously filed by the
Reporting Persons with respect to the Common Stock, $.10 par value (the "Common
Stock"), of MasTec, Inc., a Florida corporation (the "Issuer").

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER

         As of the date of this Amendment No. 3, the Reporting Persons
beneficially owned the following shares of Common Stock:

                                    AMOUNT OF SHARES                            
               NAME                BENEFICIALLY OWNED    PERCENTAGE OF CLASS(1)
               ----                ------------------    ----------------------
Jorge L. Mas Canosa Holdings I
    Limited Partnership                 7,515,811               24.2%

Jorge Mas Holdings I Limited
    Partnership                         5,587,311               18.0%

Jorge Mas(2)                           13,416,545               43.2%
------------------------
(1)      Based on 31,090,563 shares of Common Stock which includes (1)
         30,922,737 shares of Common Stock outstanding on March 1, 2000 (as
         confirmed by representatives of the Issuer) and (2) options to purchase
         167,826 shares owned directly by Jorge Mas and exercisable within 60
         days of this report on Schedule 13D.
(2)      The shares beneficially owned by Jorge Mas include: (1) 7,515,811
         shares held by the Family Partnership, a limited partnership which is
         controlled by Jorge L. Mas Holdings Corporation, the sole general
         partner of the Family Partnership, of which Jorge Mas is an officer and
         shareholder and the sole director; (2) 5,587,311 shares held by Jorge
         Mas Holdings, a limited partnership which is controlled by Jorge Mas
         Holdings Corporation, the sole general partner of Jorge Mas Holdings,
         of which Jorge Mas is the sole officer, director and shareholder; (3)
         145,597 shares owned directly by Jorge Mas; and (4) options to purchase
         167,826 shares owned directly by Jorge Mas and exercisable within 60
         days of this report on Schedule 13D.

         Except as set forth below, there have been no transactions by the
Reporting Persons effected during the past 60 days of this report.

1.       On February 3, 2000, Jorge Mas exercised options to purchase 57,140
         shares of Common Stock at a price of $9.8084 per share which options
         were to expire on that day, and, in connection with such exercise, sold
         1,600 of the acquired shares at a price of $ 48.25 per share and an
         additional 10,100 of the acquired shares at a price of $48.125 to pay
         the exercise price of the options.

2.       On March 1, 2000, Jorge Mas borrowed 375,000 shares of Common Stock
         from the Family Partnership, and sold such shares in an open market
         transaction at a price of $53 per share upon the exercise of an
         over-allotment option granted by Mr. Mas to certain underwriters in
         connection with the Issuer's public offering of Common Stock.

                                     Page 5


<PAGE>

ITEM 6.  CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
         TO SECURITIES OF THE ISSUER.

1.       Pursuant to Mr. Mas's borrowing of 375,000 shares of the Common Stock
         from the Family Partnership, as described above, Mr. Mas entered into a
         Securities Loan Agreement, dated February 24, 2000, with the Family
         Partnership (included as Exhibit 6 to this Amendment No. 3 to Schedule
         13D) (the "Loan Agreement"). Under the Loan Agreement, Mr. Mas is
         obligated to repay the Family Partnership by delivering to the Family
         Partnership shares of Common Stock equal in number to the borrowed
         shares five days after the demand by the Family Partnership and, upon
         demand, to pay to the Family Partnership amounts equal to any dividends
         and other distributions on the borrowed shares. The Family Partnership
         may also, from time to time, demand a pledge of collateral by Mr. Mas
         to secure his obligations to repay the borrowed shares to the Family
         Partnership.

2.       With respect to the Issuer's public offering of Common Stock, Mr. Mas
         entered into a customary agreement with the underwriters of the
         Issuer's public offering (included as Exhibit 7 to this Amendment No. 3
         to Schedule 13D) whereby he agreed to refrain from certain dispositions
         of the Common Stock for a period of 90 days after the date of the final
         prospectus relating to the offering.

         The descriptions of the foregoing agreements are qualified in their
         entirety by reference to the full text of such agreements, each of
         which is filed as an exhibit hereto and incorporated by this reference
         herein.

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.

1.       Joint Filing Agreement, dated September 23, 1998, by and among Jorge
         Mas, Jorge L. Mas Canosa Holdings I Limited Partnership and Jorge Mas
         Holdings I Limited Partnership.*

2.       Purchase and Sale Agreement, dated June 19, 1998, by and among Jorge
         Mas, as trustee of the Marital Trust #2 under the will of Jorge L. Mas
         Canosa, and Jorge Mas, Juan Carlos Mas, and Jose Ramon Mas.*

3.       Form of Promissory Note, dated July 21, 1998, by and between Jorge Mas,
         Juan Carlos Mas, and Jose Ramon Mas and the Marital Trust #2.*

4.       Form of Pledge and Security Agreement, dated July 21, 1998, by and
         between Jorge Mas, Juan Carlos Mas, and Jose Ramon Mas and the Marital
         Trust #2.*

5.       Form of Assignment, Acceptance, Agreement to be Bound and General
         Partner Consent, dated July 21, 1998, by and among Jorge Mas, Juan
         Carlos Mas, and Jose Ramon Mas, the Marital Trust #2 and Jorge L. Mas
         Canosa Holdings Corporation.*

6.       Securities Loan Agreement, dated February 24, 2000, between Jorge L.
         Mas Canosa Holdings I Limited Partnership and Jorge Mas.

7.       Lock-up Agreement, dated February 24, 2000, by and among Jorge L. Mas
         Canosa Holdings I Limited Partnership and Morgan Stanley & Co.
         Incorporated, Morgan Stanley & Co. International Limited, Jefferies &
         Company, Inc., Jefferies International Limited, and Morgan Keegan &
         Company, Inc.
_____________________________________
*Previously filed.

                                     Page 6


<PAGE>

                                   SIGNATURES

         After reasonable inquiry and to the best of the undersigned's knowledge
and belief, the undersigned certify that the information set forth in this
Amendment No. 3 to Schedule 13D is true, complete and correct.

Date: March 14, 2000                 JORGE L. MAS CANOSA HOLDINGS I LIMITED
                                     PARTNERSHIP

                                          By:    Jorge L. Mas Canosa Holdings
                                                 Corporation, general partner


                                          By:/S/ JORGE MAS, PRESIDENT
                                             ----------------------------------
                                                 Jorge Mas, President

Date: March 14, 2000                 JORGE MAS HOLDINGS I
                                     LIMITED PARTNERSHIP

                                          By:    Jorge Mas Holdings Corporation,
                                                 general partner



                                          By:/S/ JORGE MAS, PRESIDENT
                                             ----------------------------------
                                                 Jorge Mas, President

Date: March 14, 2000                  /S/ JORGE MAS
                                      -----------------------------------------
                                      JORGE MAS


                                     Page 7



<PAGE>

                                  EXHIBIT INDEX

1.       Joint Filing Agreement, dated September 23, 1998, by and among Jorge
         Mas, Jorge L. Mas Canosa Holdings I Limited Partnership and Jorge Mas
         Holdings I Limited Partnership.*

2.       Purchase and Sale Agreement, dated June 19, 1998, by and among Jorge
         Mas, as trustee of the Marital Trust #2 under the will of Jorge L. Mas
         Canosa, and Jorge Mas, Juan Carlos Mas, and Jose Ramon Mas.*

3.       Form of Promissory Note, dated July 21, 1998, by and between Jorge Mas,
         Juan Carlos Mas, and Jose Ramon Mas and the Marital Trust #2.*

4.       Form of Pledge and Security Agreement, dated July 21, 1998, by and
         between Jorge Mas, Juan Carlos Mas, and Jose Ramon Mas and the Marital
         Trust #2.*

5.       Form of Assignment, Acceptance, Agreement to be Bound and General
         Partner Consent, dated July 21, 1998, by and among Jorge Mas, Juan
         Carlos Mas, and Jose Ramon Mas and the Marital Trust #2 and Jorge L.
         Mas Canosa Holdings Corporation.*

6.       Securities Loan Agreement, dated February 24, 2000, between Jorge L.
         Mas Canosa Holdings I Limited Partnership and Jorge Mas.

7.       Lock-up Agreement, dated February 24, 2000, by and among Jorge L. Mas
         Canosa Holdings I Limited Partnership and Morgan Stanley & Co.
         Incorporated, Morgan Stanley & Co. International Limited, Jefferies &
         Company, Inc., Jefferies International Limited, and Morgan Keegan &
         Company, Inc.
_____________________________________
*Previously filed.

                                     Page 8






                                                                       EXHIBIT 6

                            SECURITIES LOAN AGREEMENT

         This Securities Loan Agreement (the "Agreement") is made as of the 24th
day of February, 2000, between Jorge L. Mas Canosa Holdings I Limited
Partnership, as lender (the "Lender"), and Jorge Mas, as borrower (the
"Borrower").

         Borrower and Lender acknowledge that pursuant to this Agreement, Lender
has delivered to the U.S. Underwriters on behalf of Borrower in accordance with
the Underwriting Agreement 375,000 shares of common stock of MasTec, Inc. (the
"Shares") represented by the certificate(s) identified on Exhibit A attached
hereto. The Shares are loaned (the "Loan") by Lender to Borrower pursuant to
this Agreement upon the following terms. Lender acknowledges the receipt of
$30,000 paid by Borrower to Lender as a premium for the Loan. The purpose of the
Loan is to provide the Shares to Borrower for delivery for sale by Borrower in
accordance with the Underwriting Agreement.

         1. TRANSFER OF RIGHTS. Borrower may sell, assign, convey and transfer
all (but not personally possess or exercise any) rights incident to the Shares,
and ownership thereof, including (without limitation) the rights, if any, to
vote (and give proxies to vote) the Shares at any meeting of shareholders, to
sell, pledge or hypothecate
 the Shares upon any terms and conditions, to receive
and have sole use and benefit of all dividends and other distributions accruing
or declared with respect to the Shares after the date of this Agreement, and all
other rights, powers, offices and privileges of an owner of the Shares as the
same exist without reference to this Agreement.


<PAGE>

         2. RETURN OF STOCK. Borrower will return pursuant to this Agreement
(the "return") identical securities to Lender within five days after Lender's
demand given to Borrower pursuant to this paragraph.

         3. ADDITIONAL PAYMENTS. Borrower will also pay to Lender from time to
time but not later than five days after Lender's demand given to Borrower
amounts equivalent to all interest, dividends, and other distributions (other
than identical securities) which the owner of identical securities subject to
return from time to time pursuant to the preceding paragraph is entitled to
receive during the period beginning on the date of this Agreement and ending
with the return of such securities pursuant to the preceding paragraph.

         4. LENDER'S RISK AND GAIN. This Agreement shall not reduce the Lender's
risk of loss or opportunity for gain with respect to the identical securities.
This Agreement is intended to satisfy the requirements of ss.1058(b) of the Code
and of any Treasury Regulations promulgated thereunder. This Agreement shall be
interpreted, construed and applied in accordance with the intent expressed in
the two immediately preceding sentences.

         5. SECURITY. Within five days after Lender's demand given to Borrower
from time to time, Borrower shall deliver as collateral security for the Loan
(the "pledge"), upon such reasonable terms as Lender shall specify, cash or
identical securities (as specified by Borrower) in such amount which together
with any other collateral pledged by Borrower pursuant to this paragraph does
not exceed the fair market value of such identical securities as would then be
subject to return to Lender if Lender then made demand for the full and final
return of identical securities pursuant to paragraph 2.

         6. FURTHER COOPERATION. Each of Borrower and Lender agree to execute
and deliver such documents and instruments, including modifications of this
Agreement, as the other may


<PAGE>


reasonably request to further accomplish the Loan, the return, the pledge, and
the intentions expressed in paragraph 4.

         7. DEFINITIONS. In this Agreement,

                  a.       The "Code" means the Internal Revenue Code of 1986,
                           as amended, and reference to any section of the Code
                           includes reference to any successor provisions of the
                           Code corresponding to such section.

                  b.       The term "identical securities" means 375,000 shares
                           of common stock of MasTec, Inc., provided, if prior
                           to the return there is a merger, recapitalization or
                           reorganization of the issuer of identical securities,
                           any securities issued with respect to or in exchange
                           for identical securities pursuant to such merger,
                           recapitalization or reorganization shall also be
                           identical securities.

                  c.       The term "securities" has the meaning given such term
                           in ss.1236(c) of the Code.

                  d.       The "Underwriting Agreement" means that certain
                           agreement dated February ___, 2000, among MasTec,
                           Inc., the Borrower, and Morgan Stanley & Co.
                           Incorporated, Jefferies & Company, Inc., and Morgan
                           Keegan & Company, Inc., as representatives of the
                           several underwriters, concerning the sale of shares
                           of common stock of MasTec, Inc.; and the term "U.S.
                           Underwriters" has the same meaning as in the
                           Underwriting Agreement.

         8. NOTICES. All notices, demands or requests provided for or permitted
to be given pursuant to this Agreement must be in writing and shall be delivered
or sent by personal delivery or overnight delivery service to the parties as
follows:

            Borrower:         Jorge Mas

                              3155 N.W. 77th Avenue
                              Miami, Florida  33122

            Lender:           Jorge L. Mas Canosa Holdings I Limited Partnership
                              2716 East 5th Street

                              Austin, Texas  78702



<PAGE>


A notice shall be deemed given one day after its delivery to the address for the
respective party as provided in this paragraph. Any person may change his
address, and additional persons may be added, by notifying all of the other
parties in writing in the manner set forth.

         9. REMEDIES. In addition to any remedies which may be provided in this
Agreement, or by law, in the event of a breach of this Agreement by any party,
the other party shall have the right of specific performance. In the event of
any dispute or litigation between the parties to enforce the provisions of, or
with respect to this Agreement, the prevailing party shall be entitled to
reasonable attorney's fees and court costs, including those for appellate
proceedings and for paralegals and similar persons.

         10. ENTIRE AGREEMENT. This Agreement contains the sole and entire
agreement between the parties with respect to its subject matter and supersedes
any and all other prior written or oral agreements between them with respect to
such subject matter.

         11. AMENDMENT. No amendment or modification of this Agreement shall be
valid unless in writing and duly executed by the parties affected by the
amendment or modification. 

         12. BINDING EFFECT. This Agreement shall be binding upon and inure to
the benefit of the parties and their respective representatives, successors and
assigns.

         13. GOVERNING LAW. Subject to paragraph 4., this Agreement and the
interpretation of its terms shall be governed by the laws of the State of
Florida, without application of conflicts of law principles.


<PAGE>

         The parties have executed this Agreement as of the date set forth
above.

                                   JORGE L. MAS CANOSA HOLDINGS I
                                   LIMITED PARTNERSHIP, lender

                                   By: Jorge L. Mas Canosa Holdings Corporation,
                                       general partner

                                   By: /s/ Juan Carlos Mas
                                      ------------------------------------------
                                       Juan Carlos Mas, its Vice President


                                       /s/ Jorge Mas
                                      ------------------------------------------
                                       Jorge Mas, Borrower



<PAGE>



                                    EXHIBIT A

         The following certificates representing shares of common stock of
MasTec, Inc. have been delivered hereunder by Lender on behalf of Borrower in
accordance with the Underwriting Agreement:

                  CERTIFICATE NO(S).                       SHARES

                  MAS 11318                                100,000


                  MAS 11291                                275,000


                  Witness our signatures.

                                   JORGE L. MAS CANOSA HOLDINGS I
                                   LIMITED PARTNERSHIP, Lender

                                   By: Jorge L. Mas Canosa Holdings Corporation,
                                       general partner


                                   By: 
                                      ------------------------------------------
                                       Juan Carlos Mas, its Vice President



                                      ------------------------------------------
                                       Jorge Mas, Borrower




                                                                       EXHIBIT 7

February 24, 2000


Morgan Stanley & Co. Incorporated
Jefferies & Company, Inc.
Morgan Keegan & Company, Inc.
c/o Morgan Stanley & Co. Incorporated
1585 Broadway
New York, NY  10036

Morgan Stanley & Co. International Limited
Jefferies International Limited
Morgan Keegan & Company, Inc.
c/o Morgan Stanley & Co. International Limited
25 Cabot Square
Canary Wharf
London E14 4QA
England

Dear Sirs and Mesdames:

The undersigned understands that Morgan Stanley & Co. Incorporated ("Morgan
Stanley"), Morgan Stanley & Co. International Limited ("MSIL"), Jefferies &
Company, Inc., Jefferies International Limited, and Morgan Keegan & Company,
Inc. propose to enter into an Underwriting Agreement (the "Underwriting
Agreement") with MasTec, Inc., a Florida corporation (the "Company"), and a
certain selling shareholder named therein (the "Selling Shareholder") providing
for the public offering (the "Public Offering") by the several Underwriters,
including Morgan Stanley and MSIL (the "Underwriters") of 2,500,000 shares (the
"Shares") of the common stock, $.10 par value, of the Company (the "Common
Stock").

To induce the Underwriters that may participate in the Public Offering to
continue their efforts in connection with the Public Offering, the undersigned
hereby
 agrees that, without the prior written consent of Morgan Stanley on
behalf of the Underwriters, the undersigned will not, during the period
commencing on the date hereof and ending 90 days after the date of the final
prospectus relating to the Public Offering (the "Prospectus"), (1) offer,
pledge, sell, contract to sell, sell any option or contract to purchase,
purchase any option or contract to sell, grant any option, right or warrant to
purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any
shares of Common Stock or any securities convertible into or exercisable or
exchangeable for Common Stock, or (2) enter into any swap or other arrangement
that transfers to another, in whole or in part, any of the economic consequences
of ownership of the Common Stock, whether any such transaction described in
clause (1) or (2) above is to be settled by delivery of Common Stock or such
other securities, in cash or otherwise. The foregoing sentence



<PAGE>


shall not apply to (a) the sale of any Shares to the Underwriters pursuant to
the Underwriting Agreement, (b) the issuance of common stock by the Company upon
the exercise of an option or warrant or the conversion of a security outstanding
on the date of the Prospectus, of which the underwriters have been advised in
writing, (c) any private placement of shares of common stock to a strategic
investor who agrees to be bound by the terms of this agreement, (d) the issuance
of shares of common stock by the Company as consideration for the purchase by it
of any business or asset, (e) transactions relating to shares of Common Stock or
other securities acquired in open market transactions after the completion of
the Public Offering, (f) transactions relating to shares of Common Stock that do
not result in a change in the beneficial owner of such shares or (g) any shares
of Common Stock currently pledged to Ocean Bank unless such shares are released
from the pledge and are returned to the pledgor, in which case the shares will
become subject to this letter. In addition, the undersigned agrees that, without
the prior written consent of Morgan Stanley on behalf of the Underwriters, the
undersigned will not, during the period commencing on the date hereof and ending
90 days after the date of the Prospectus, make any demand for or exercise any
right with respect to, the registration of any shares of Common Stock or any
security convertible into or exercisable or exchangeable for Common Stock.

Whether or not the Public Offering actually occurs depends on a number of
factors, including market conditions. Any Public Offering will only be made
pursuant to an Underwriting Agreement, the terms of which are subject to
negotiation between the Company, the Selling Shareholder and the Underwriters.

Very truly yours,

                                     JORGE L. MAS CANOSA HOLDINGS I
                                     LIMITED PARTNERSHIP,
                                     a Texas limited partnership


                                           By: Its Sole General Partner,
                                           JORGE L. MAS CANOSA
                                           HOLDINGS CORPORATION,
                                           a Texas corporation

                                     By:   /S/ JORGE MAS
                                        ---------------------------------------
                                           Jorge Mas, President