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                                             Filed Pursuant to Rule 424(b)(3)
                                                   Registration No. 333-34860

PROSPECTUS SUPPLEMENT
(To Prospectus, dated May 8, 2000)

                                VERTICALNET, INC.

                                3,905,262 Shares

                                  Common Stock

                         -------------------------------

         This document supplements the prospectus, dated May 8, 2000, relating
to resale by the selling shareholders identified in the prospectus, as
supplemented, of 3,905,262 shares of our common stock issued in connection with
our acquisitions of Tradeum, Inc., National Career Search, Inc., HRLibrary.com,
Inc. and the assets of Leasend.com, Inc. and R.W. Electronics, LLC. This
prospectus supplement is incorporated by reference into the prospectus. On
September 19, 2000, the last sale price of our common stock on the Nasdaq
National Market was $40.00 per share. Our common stock is traded under the
symbol "VERT."

         The following table sets forth information, as of September 19, 2000,
regarding the selling shareholder listed below. The selling shareholder, which
acquired the shares referenced below from Julian Ungar, has not had a material
relationship with VerticalNet within the past three years other than as a result
of the ownership of our shares or other securities.

                      SHARES BENEFICIALLY
                          OWNED BEFORE           SHARES OFFERED
      NAME                  OFFERING                 HEREBY
------------------    --------------------       --------------

Ellis Enterprises             2,286                  2,286
42A Waterloo Road
London, England
NW27UF

         The selling shareholder information set forth above replaces and
supersedes the information regarding Julian Ungar that was previously filed and
included in the "Selling Shareholders" section of the prospectus.

         SEE "RISK FACTORS" BEGINNING ON PAGE 8 OF THE PROSPECTUS FOR A
DESCRIPTION OF CERTAIN FACTORS THAT SHOULD BE CONSIDERED BY PROSPECTIVE
INVESTORS.

         Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or passed upon the
adequacy or accuracy of this prospectus. Any representation to the contrary is a
criminal offense.

         The date of this prospectus supplement is September 20, 2000.