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                                                                     EXHIBIT 5.1


                  REBOUL, MACMURRAY, HEWITT, MAYNARD & KRISTOL
                              45 Rockefeller Plaza
                            New York, New York 10111


                                   June , 2000



Lexent Inc.
Three New York Plaza
New York, New York 10004

Ladies and Gentlemen:

            We have acted as counsel to Lexent Inc., a Delaware corporation (the
"Company"), in connection with the preparation and filing of the Registration
Statement (File No. 333-30660) of the Company on Form S-1, as amended (the
"Registration Statement") under the Securities Act of 1933, as amended (the
"Securities Act"), relating to the public offering (the "Offering") by the
Company of up to 14,375,000 shares (including 1,875,000 shares subject to
over-allotment options) of Common Stock, $.001 par value, of the Company (the
"Common Stock").

            In that connection, we have participated in the preparation of the
Registration Statement, including the Prospectus contained therein (the
"Prospectus") and have reviewed certain corporate proceedings. In addition, we
have examined originals or copies certified or otherwise identified to our
satisfaction, of such corporate records, agreements, documents and other
instruments, and such certificates or comparable documents of public officials
and of officers and representatives of the Company, as we have deemed necessary
to form a basis for the opinions hereinafter set forth.

            In such examination, we have assumed the genuineness of all
signatures, the legal capacity of natural persons, the authenticity of all
documents submitted to us as originals, the conformity to original documents of
all documents submitted to us as certified or photostatic copies and the
authenticity of all such latter documents. As to all questions of fact material
to this opinion that have not been independently established, we have relied
upon certificates or comparable documents of officers and representatives of the
Company.
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            Based on the foregoing, and subject to the qualifications stated
herein, we are of the opinion that:

            1. The Company is a corporation duly incorporated and validly
existing under the laws of the State of Delaware.

            2. The shares of Common Stock to be registered for sale by the
Company under the Registration Statement have been duly authorized and, when
issued and paid for as contemplated by the Prospectus, will be validly issued,
fully paid and non-assessable.

            The opinions expressed herein are limited to the corporate laws of
the State of Delaware and we express no opinion as to the effect on the matters
covered by this letter of the laws of any other jurisdiction.

            The opinions expressed herein are rendered solely for your benefit
in connection with the transactions described herein. These opinions may not be
used or relied upon by any other person, nor may this letter or any copies
thereof be furnished to a third party, filed with a governmental agency, quoted
cited or otherwise referred to without our prior written consent.

            We hereby consent to the filing of this opinion as Exhibit 5.1 to
the Registration Statement. In giving the foregoing consent, we do not admit
that we are in the category of persons whose consent is required under Section 7
of the Securities Act or the rules and regulations of the Securities and
Exchange Commission promulgated thereunder.

            We also consent to the incorporation by reference of this opinion in
a related registration statement filed by the Company pursuant to Rule 462(b)
under the Securities Act.

                                Very truly yours,


                                Reboul, MacMurray, Hewitt
                                 Maynard & Kustol

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