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                                                                   EXHIBIT 10.21
                                                                                
                           AMENDMENT NO. 1 TO LEASE
                           ------------------------
                   
                                        
     This Amendment No. 1 is made as of this 29th day of December, 1998 by and
between G & H Post, LLC, a New Hampshire Limited Liability Company and PC
Connection, Inc., a Delaware Corporation (successor to PC Connection, Inc., a
New Hampshire corporation) to that certain Amended and Restated Lease dated
December 29, 1997 pertaining to property located at Post Road Plaza, Route 101A,
Merrimack, New Hampshire (the "Lease").

     For good and valuable consideration received the parties agree as follows:

     1.   Section 1.1 of the Lease shall be amended by increasing the square
          footage of the Premises from 102,874 square feet to 113,928 square
          feet.

     2.   Section 3.2 of the Lease shall be replaced in its entirety with the
          following:

          The base rent ("Base Rent") for the years 1 through 5 of the term
          hereof shall be the sum of Eight Dollars ($8.00) per square foot or
          Nine Hundred Eleven Thousand, Four Hundred Twenty-Four Dollars
          ($911,424) per year payable monthly, in advance, in installments of
          Seventy-Five Thousand, Nine Hundred Fifty-Two Dollars ($75,952) (the
          "Base Rent"). The Base Rent for years 6 through 10 of the term hereof
          shall be the sum of Nine Dollars ($9.00) per square foot or One
          Million, Twenty-Five Thousand, Three Hundred Fifty-Two Dollars
          ($1,025,352) per year payable monthly, in advance in installments of
          Eight-Five Thousand, Four Hundred Forty-Six ($85,446). The Base Rent
          for years 11 through 15 of the term hereof shall be the sum of Ten
          Dollars ($10.00) per square foot or One Million, One Hundred Thirty-
          Nine Thousand, Two Hundred Eighty ($1,139,280) per year payable
          monthly, in advance, in installments of Ninety-Four Thousand, Nine
          Hundred Forty Dollars ($94,940).

3.   In all other respects the Lease shall remain in full force and effect.

Executed this 29th day of December, 1998 to be effective as of December 1, 1998.

                                        LESSOR; G & H POST, LLC


/s/  Jack Ferguson                      By:  /s/  Patricia Gallup
----------------------------                 -------------------------------
Witness                                      Its:
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                                        LESSEE: PC CONNECTION, INC.


/s/ Jack L. Ferguson                    By: /s/ Mark A. Gavin
---------------------                      ----------------------------------
Witness                                     Its: Chief Financial Officer



STATE OF NEW HAMPSHIRE
COUNTY OF HILLSBOROUGH


    On this the 29th day of December, 1998, before me, the undersigned officer,
personally appeared Patricia Gallup, who acknowledged him/herself to be a Member
of G&H Post, LLC, a New Hampshire limited liability company, and as such
executed the within instrument for the purposes therein contained on behalf of
the company.

                                            /s/ Eileen A. Gagnon
                                            -----------------------------------
                                            Notary Public/Justice of the Peace
                                            My Commission Expires:
                                             August 28, 1999


STATE OF NEW HAMPSHIRE
COUNTY OF HILLSBOROUGH


    On this the 29th day of December, 1998, before me, the undersigned officer,
personally appeared Mark A. Gavin, who acknowledged him/herself to be Chief
Financial Officer of PC Connection, Inc, a Delaware corporation, and as such
executed the within instrument for the purposes therein contained on behalf of
the corporation.


                                            /s/ Eileen A. Gagnon
                                            ---------------------------------
                                            Notary Public/Justice of the Peace
                                            My Commission Expires:
                                            August 28, 1999
