EXHIBIT 5.1 LAW OFFICES STEARNS WEAVER MILLER WEISSLER ALHADEFF & SITTERSON, P.A. MUSEUM TOWER 150 WEST FLAGLER STREET MIAMI, FLORIDA 33130 --------- MIAMI (305) 789-3200o BROWARD (954) 463-5440 FAX (305) 789-3395 WWW.STEARNSWEAVER.COM E. RICHARD ALHADEFF LISHA D. HOGUE PATRICIA A. REDMOND OWEN S. FREED LOUISE JACOWITZ ALLEN ALICE R. HUNEYCUTT ELIZABETH G. RICE SENIOR COUNSEL STUART D. AMES RICHARD B. JACKSON GLENN M. RISSMAN ALEXANDER ANGUEIRA THEODORE A. JEWELL KEITH E. ROUNSAVILLE DAVID M. SMITH LAWRENCE J. BAILIN SHARON LEE JOHNSON STEVEN D. RUBIN LAND USE CONSULTANT ANA T. BARNETT MICHAEL I. KEYES MIMI L. SALL PATRICK A. BARRY ROBERT T. KOFMAN NICOLE S. SAYFIE SHAWN BAYNE CHAD K. LANG RICHARD E. SCHATZ TAMPA OFFICE SUSAN FLEMING BENNETT FRANK J. LOPEZ DAVID M. SEIFER SUITE 2200 LISA K. BERG TERRY M. LOVELL JOSE G. SEPULVEDA SUNTRUST FINANCIAL CENTRE MARK J. BERNET JOY SPILLIS LUNDEEN JAY B. SHAPIRO 401 EAST JACKSON STREET HANS C. BEYER GEOFFREY MacDONALD MARTIN S. SIMKOVIC TAMPA, FLORIDA 33602 RICHARD I. BLINDERMAN MONA E. MARKUS CURTIS H. SITTERSON ---------- MATTHEW W. BUTTRICK BRIAN J. McDONOUGH MARK D. SOLOV (813) 223-4800 JENNIFER STEARNS BUTTRICK ANTONIO R. MENENDEZ EUGENE E. STEARNS PETER L. DESIDERIO FRANCISCO J. MENENDEZ THOMAS T. STEELE MARK P. DIKEMAN ALISON W. MILLER BRADFORD SWING FORT LAUDERDALE OFFICE DREW M. DILLWORTH VICKI LYNN MONROE SUSAN J. TOEPFER SUITE 1900 SHARON QUINN DIXON HAROLD D. MOOREFIELD, JR. ANNETTE TORRES 200 EAST BROWARD BOULEVARD ALAN H. FEIN JIMMY L. MORALES DENNIS R. TURNER FORT LAUDERDALE, FLORIDA 33301 ANGELO M. FILIPPI JOHN N. MURATIDES RONALD L. WEAVER ----------- ELISE FRIEDBAUER JOHN K. OLSON ROBERT I. WEISSLER (954) 462-9500 ROBERT E. GALLAGHER, JR. JEFFREY A. NORMAN PATRICIA G. WELLES CHAVA E. GENET KARA E. PLUNKETT MARTIN B. WOODS LATASHA A. GETHERS DAVID C. POLLACK PATRICIA K. GREEN DARRIN J. QUAM JOSEPH K. HALL JOHN M. RAWICZ June 9, 2000 Jose Sariego, Esq. Senior Vice President - General Counsel MasTec, Inc. 3155 N.W. 77th Avenue Miami, Florida 33122-1205 Re: MasTec, Inc. Registration Statement on Form S-8 ---------------------------------- Dear Mr. Sariego: As counsel to MasTec, Inc., a Florida corporation (the "Corporation"), we have examined the Articles of Incorporation and Bylaws of the Corporation, as well as such other documents and proceedings as we have considered necessary for the purposes of this opinion. We have also examined and are familiar with the Corporation's Registration Statement on Form S-8 (the "Registration Statement"), filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended, relating to 1,000,000 shares of the Corporation's common stock, par value $.10 per share (the "Common Stock"), issuable by the Corporation pursuant to the Corporation's 1994 Incentive Stock Option Plan (the "Plan"). In rendering this opinion, we have assumed, without independent investigation: (i) the authenticity of all documents submitted to us as originals; (ii) the conformity to original documents of all documents submitted to us as certified or photostatic copies and (iii) the genuineness of all signatures. In addition, as to questions of fact material to the opinions expressed herein, we have relied upon such certificates of public officials, corporate agents and officers of the Corporation and such other certificates as we deemed relevant. Based upon the foregoing, and having regard to legal considerations which we deem relevant, we are of the opinion that following the issuance and delivery of the Common Stock by the Corporation under the Plan, against payment of adequate consideration therefor to the Corporation in accordance with the terms of the Plan, the Common Stock will be validly issued, fully paid and non-assessable. This opinion is intended solely for the Corporation's use in connection with the registration of the Common Stock and may not be relied upon for any other purpose or by any other person. This opinion may not be quoted in whole or in part or otherwise referred to or furnished to any other person except in response to a valid subpoena. This opinion is limited to the matters expressly stated herein, and no opinion is implied or may be inferred beyond the matters expressly stated herein. This opinion is rendered as of the date hereof, and we assume no obligation to update or supplement such opinion to reflect any facts or circumstances that may hereafter come to our attention or any changes in facts or law that may hereafter occur. We hereby consent to the inclusion of this opinion letter as an exhibit to the Registration Statement. Very truly yours, /s/ Stearns Weaver Miller Weissler Alhadeff & Sitterson, P.A. STEARNS WEAVER MILLER WEISSLER ALHADEFF & SITTERSON, P.A.