Exhibit 10.5

   SECOND ADDENDUM TO SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

     This Second Addendum To Series C Convertible Preferred Stock Purchase
Agreement (this "Addendum") is made as of the 6th day of February, 2001 by and
among InPhonic, Inc., a Delaware corporation (the "Company"), Sterling
Communications, Inc., a wholly owned subsidiary of the Company, ("Sterling"),
each purchaser set forth on Exhibit A hereto (each a "Purchaser" and,
collectively, the "Purchasers"), and the persons and entities listed on the
Schedule of Additional Investors attached hereto as Exhibit B (each an
"Additional Investor" and, collectively the "Additional Investors").

                                    Recitals

     On October 13, 2000, the Company, Sterling and the Purchasers entered into
a Series C Preferred Stock Purchase Agreement (the "Purchase Agreement"). The
Purchase Agreement provides in Section 2.3 thereof that additional investors
may, under conditions set forth therein, become parties to the Purchase
Agreement by executing this Addendum. Capitalized terms not defined in this
Addendum shall have the meaning set forth in the Purchase Agreement.

                                    Agreement

     In consideration of the mutual promises, covenants and conditions
hereinafter set forth, the parties hereto mutually agree as follows:

     1.   Agreement to Sell and Purchase.

          1.1.    Sale of Preferred Stock. Subject to the terms and conditions
hereof, at the Closing (as defined in Section 2.1 hereof), the Company will
issue and sell to the Additional Investors, and such Additional Investors agree
to purchase from the Company, that number of shares of Series C Preferred Stock
specified opposite such Additional Investor's name on Exhibit B hereto (the
"Additional Shares"), at a purchase price of $1.039401493 per share. Each
Additional Investor, by his, her or its signature hereto, shall hereby (i)
become a party to the Purchase Agreement, (ii) be considered a "Purchaser" for
all purposes under the Purchase Agreement and (iii) have all the rights and
obligations of a Purchaser thereunder. The Additional Shares acquired by the
Additional Investors hereunder shall be considered "Shares" for all purposes
under the Purchase Agreement, as amended.

          1.2     Warrant. The Company shall issue to each Additional Investor a

Warrant, a form of which has been attached hereto as Exhibit C, pursuant to
which each Additional Investor may purchase the number of shares of Series C
Preferred Stock as set forth on Exhibit D.

     2.   Closing; Delivery.



          2.1     Closing. The closing of the purchase and sale of the
Additional Shares hereunder (the "Closing") shall be held at the offices of
Piper Marbury Rudnick & Wolfe LLP in Washington, DC, at 10:00 a.m. Eastern
Standard Time on February 6, 2001, or at such other time and place as the
Company and the Additional Investors mutually agree.

          2.2     Delivery. At the Closing, the Company will deliver to each
Additional Investor a certificate representing the number of Additional Shares
set forth opposite such Additional Investor's name on Exhibit B and a warrant
representing the number of underlying shares set forth opposite such Additional
Investor's name on Exhibit D, against payment of the purchase price therefor by
the Additional Investor by check made payable to the Company, wire transfer, or
cancellation of indebtedness or any combination of the foregoing.

          2.3     Amendment to Purchase  Agreement.  Section 2.3 of the Purchase
Agreement is hereby  amended by deleting the section in its entirety and
replacing it as follows:

     "At any time on or before one-hundred twenty (120) days following the
     Initial Closing, the Company may sell up to the balance of the authorized
     shares of Series C Stock not sold at the Initial Closing to such persons
     and entities as may be approved by the Board of Directors of the Company;
     provided, that each Additional Investor shall be required to execute an
     addendum to this Agreement substantially in the form attached hereto as
     Exhibit C (the "Addendum"). All such sales shall be made on the terms and
     conditions set forth in this Agreement, including, without limitation, the
     representations and warranties made by such Purchasers as set forth in
     Section 4. All shares sold pursuant to this Section 2.3 shall be deemed to
     be "Shares" for all purposes under this Agreement and any purchasers
     thereof shall be deemed to be "Purchasers" for all purposes under this
     Agreement. The subsequent closing of the sale and purchase of the Shares
     pursuant to this Section 2.3 (the "Subsequent Closing") shall take place at
     the offices of Piper Marbury Rudnick & Wolfe LLP, 1200 19th Street, N.W.,
     Washington, DC 20036 or at such other place as the Company and the
     Additional Investors may mutually agree."

     3.   Disclosure.

          3.1     Disclosure.  The Additional Investors hereby acknowledge
receipt of the Purchase Agreement and the exhibits thereto.  The Company affirms
to the Additional Investors that:

                  (a)    The representations and warranties of the Company set
forth in Section 3 of the Purchase Agreement were true and accurate when made;

                  (b)    Those representations and warranties, which are
incorporated herein by reference and made a part hereof, remain true and
accurate in all material respects as of the date hereof, except (A) for changes
resulting from the transactions contemplated in the Purchase Agreement and (B)
as set forth in the Schedule of Exceptions attached hereto as Exhibit E.

                                       -2-



                  (c)    The conditions to closing set forth in Section 5.1 of
the Purchase Agreement and in Section 5 hereof have been satisfied.

     4.   Representations and Warranties of Additional Investors.

     Each Additional Investor acknowledges that such Additional Investor has
reviewed the representations and warranties set forth in Section 4 of the
Purchase Agreement and affirms to the Company that such representations and
warranties, which are incorporated herein by reference and made a part hereof,
are true and correct as of the date hereof as they relate to such Additional
Investor's purchase of the Additional Shares hereunder.

     5.   Conditions to Additional Investor's Obligations at Closing.

     The obligation of each Additional Investor to purchase the Additional
Shares at the Closing is subject to the fulfillment to such Additional
Investor's satisfaction at or prior to the Closing of the following conditions:

          5.1  Representations and Warranties Correct; Performance of
Obligations. The representations and warranties made by the Company in Section 3
hereof shall be true and correct when made, and shall be true and correct on the
date of the Closing with the same force and effect as if they had been made on
and as of said date, subject to changes contemplated by this Addendum; and the
Company shall have performed all obligations and conditions herein required to
be performed or observed by it at or prior to the Closing.

     5.2  Consents and Waivers. The Company shall have obtained any and all
consents and waivers necessary or appropriate for consummation of the
transactions contemplated by this Addendum.

     6.   Conditions to Company's Obligations at Closing.

     The obligation of the Company to issue and sell the Additional Shares to an
Additional Investor is subject to the fulfillment at or before the Closing of
each of the following conditions:

          6.1  Representations and Warranties. The representations and
warranties of each such Additional Investor contained in Section 4 hereof shall
be true and correct on the date of the Closing and each such Additional Investor
shall have performed all obligations and conditions herein required to be
performed or observed by it prior to the Closing.

          6.2  Consents and Waivers. The Company shall have obtained any
and all consents and waivers necessary or appropriate for consummation of the
transactions contemplated by this Addendum.

     7.   Miscellaneous.

          7.1  Notices. All notices required or permitted hereunder shall be in
writing and shall be deemed effectively given: (i) upon personal delivery to the
party to be notified, (ii) when sent by confirmed facsimile if sent during
normal businesshours of the recipient, if not,

                                       -3-



then on the next business day; (iii) one (1) day after deposit with a nationally
recognized overnight courier, specifying next day delivery, with written
verification of receipt or (iv) five (5) days after having been sent by
registered or certified mail, return receipt requested, postage prepaid. All
communications shall be sent to the address as set forth on the signature pages
hereof or at such other address as such party may designate by written notice to
the other parties hereto.

          7.2  Governing Law. This Addendum shall be construed under Delaware
General Corporation Law as to matters of corporate law and, as to all other
matters of law, shall be governed and construed under the laws of the State of
Maryland as such laws are applied to agreements between Maryland residents
entered into and performed entirely in Maryland.

          7.3  Counterparts. This Addendum may be executed in any number
of counterparts, each of which shall be enforceable against the parties actually
executing such counterparts, and all of which together shall constitute one
instrument.

                            [Signature Pages Follow]

                                       -4-



     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the date first above written.

                                        COMPANY:

                                        INPHONIC, INC.

                                        By:    /s/ David A. Steinberg
                                               _________________________________
                                        Name:  David A. Steinberg
                                        Title: President
                                               Chief Executive Officer

                                        Address:  1010 Wisconsin Avenue, N.W.,
                                                  Suite 250
                                                  Washington, D.C.  20007

                                        STERLING:

                                        STERLING COMMUNICATIONS, INC.

                                        By:    /s/ David A. Steinberg
                                               _________________________________
                                        Name:
                                        Title:

                                        Address:  1010 Wisconsin Avenue, N.W.,
                                                  Suite 250
                                                  Washington, D.C.  20007


                                        ADDITIONAL INVESTORS

                                        CMS PEP XIV Co-Investment Subpartnership

                                        By:   /s/ Richard A. Mitchell
                                           _____________________________________
                                        Name:
                                        Title: Authorized Officer



                                        CMS Tech Co-Investment Subpartnership

                                        By: /s/ Richard A. Mitchell
                                           _____________________________________
                                        Name:
                                        Title: Authorized Officer

                                        RAF Net Ventures

                                        By: /s/ Robert S. Adelson
                                           _____________________________________
                                               Robert S. Adelson
                                               Partner

                                        /s/ Bruce C. Lindsay
                                        ________________________________________
                                        Bruce C. Lindsay



                                 INPHONIC, INC.

                             SECOND ADDENDUM TO THE
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.



                                        /s/ Ira Brind
                                        ________________________________________
                                        Ira Brind



                                 INPHONIC, INC.

                             Second Addendum to The
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.

                                        CMS PEP XIV Co-Investment Subpartnership


                                        By: /s/ Richard A. Mitchell
                                           _____________________________________
                                        Name:
                                        Title: Authorized Officer



                                 INPHONIC, INC.

                             Second Addendum to The
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.

                                        CMS Tech Co-Investment Subpartnership


                                        By: /s/ Richard A. Mitchell
                                           _____________________________________
                                        Name:
                                        Title: Authorized Officer



                                 INPHONIC, INC.

                             Second Addendum to The
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.



                                        /s/ John LaPides
                                        ________________________________________
                                        LBL Eventures, LLC



                                 INPHONIC, INC.

                             Second Addendum to The
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE


     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.



                                        /s/ Bruce C. Lindsay
                                        ________________________________________
                                        Bruce C. Lindsay



                                 INPHONIC, INC.

                             Second Addendum to the
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE




                                        Mid-Atlantic Venture Fund III, L.P.

                                        By:  MAVF III Partners, L.P., a
                                        Pennsylvania limited partnership

                                        Its: General Partner


                                        By:  MAVF III G.P., Inc., a
                                        Pennsylvania corporation

                                        Its: General Partner


                                        By: /s/ Thomas A. Smith
                                            ____________________________________
                                            Thomas A. Smith



                                 INPHONIC, INC.

                             Second Addendum to the
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.


                                        Mt. Washington Associates L.L.C.


                                        By:    /s/ Edwin M. Martin, Jr.
                                               _________________________________
                                        Name:  Edwin M. Martin, Jr.
                                        Title: _________________________________



                                 INPHONIC, INC.

                             Second Addendum to the
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.



                                        RAFNet Ventures


                                        By:    /s/ Robert Adelson
                                               _________________________________
                                        Name:  _________________________________
                                        Title: _________________________________



                                 INPHONIC, INC.

                             Second Addendum to the
             SERIES C CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                           COUNTERPART SIGNATURE PAGE



     IN WITNESS WHEREOF, the undersigned has hereunto set his hand as of the day
and year first above written.



                                        /s/ John Sculley
                                        ________________________________________
                                        John Sculley