FILED PURSUANT TO RULE 424(b)(3)
                                                REGISTRATION STATEMENT 333-55014


                              PROSPECTUS SUPPLEMENT
                      TO PROSPECTUS DATED FEBRUARY 5, 2001


                                     [LOGO]

                             USINTERNETWORKING, INC.


                                  COMMON STOCK
                        WARRANTS TO PURCHASE COMMON STOCK

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     This Prospectus Supplement supplements and amends the Prospectus dated
February 5, 2001 relating to the shares of common stock, par value $.001 per
share and warrants to purchase common stock, acquired in private placement
transactions.

     The table on page 14 of the Prospectus, which sets forth information with
respect to the Selling Security Holders and the respective amounts of shares
beneficially owned by each Selling Security Holder that may be offered under the
Prospectus (as supplemented and amended), is amended so that the following new
line items are added to the table of Selling Security Holders:


                                                                                                          
Maryland Department of Business & Economic Development.................38,937       0           38,937                    *
Pension Scheme of Flying Personnel of Swissair.........................405,176      0           405,176                0.3%
PNC Equities Corp......................................................33,765       0           107,317                   *


* Represents less than one-tenth than one percent of total outstanding shares.

     The Prospectus, together with this Prospectus Supplement, constitutes the
prospectus required to be delivered by Section 5(b) of the Securities Act of
1933, as amended, with respect to offers and sales of our common stock held by
the stockholders identified in the Prospectus. All references in the Prospectus
to "this Prospectus" are hereby amended to read "this Prospectus (as
supplemented and amended)."

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     INVESTING IN OUR SHARES OR OUR COMMON STOCK INVOLVES SUBSTANTIAL RISKS. SEE
"RISK FACTORS" BEGINNING ON PAGE 4 OF THE PROSPECTUS.

     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.

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          The date of this Prospectus Supplement is November 2, 2001.