<PAGE>

                                                                  Exhibit 10.4

                                                                 RETURN TO LPI
                                           
                                                                 MSELA No. 488
                                                           Counterpart No. 001
                                           

                   MASTER SOFTWARE/EQUIPMENT LEASE AGREEMENT 
                                         
 
MASTER SOFTWARE/EQUIPMENT LEASE AGREEMENT ("Agreement") dated as of September 
20, 1996 between LPI SOFTWARE FUNDING GROUP, INC., One Glenhardie Corporate 
Center, 1275 Drummers Lane, Wayne, PA  19087 ("Lessor") and PSINet, Inc., 510 
Huntmar Park Drive, Herndon, VA 22070 ("Lessee").


1.  LEASE 
    -----

    This Agreement specifies the general terms and conditions which 
    apply to each separate lease transaction, including renewals, between 
    Lessor and Lessee.  Each Lease ("Lease") will be a separate Lease of 
    the software and documentation ("Software") and equipment ("Equipment") 
    specified in the Lease, will substantially be in the form attached as 
    Exhibit A, will incorporate by reference all provisions of this 
    Agreement, and may specify additional provisions. 
    
    In return for Lessor paying the Software License fee and Equipment cost 
    so that the Lessee may acquire the right to use the Software and the 
    Equipment, Lessee shall pay all Lease Payments to Lessor, as well as 
    comply with all other terms and conditions of this Agreement.  A Lease 
    shall be binding upon Lessor and Lessee from the date of acceptance and 
    execution by Lessor at its office in Pennsylvania. 
    
    Software does not include any intellectual property rights vested in 
    the Software Licensor or developer.

2.  TERM 
    ----

    The term of this Agreement shall commence on the date set forth 
    above and shall continue in effect as long as any Lease remains in 
    effect.  The term of each Lease shall commence on the date the Software 
    and Equipment is accepted by Lessee, as evidenced in the Certificate of 
    Acceptance ("Commencement Date"), and shall continue for the full 
    number of periods specified in such Lease ("Initial Term") after the 
    first day of the month following the Commencement Date. 

3.  LEASE PAYMENT 
    -------------

    Lessee shall for each period pay to Lessor, without notice or 
    demand, at the office of Lessor in Wayne, Pennsylvania, or at such 
    other place as Lessor may designate, the amount specified as Lease 
    Payment in the Lease plus applicable state and local sales or use 
    taxes.  Lessee's obligation to pay shall begin on the Commencement 
    Date.  Lease Payment is due in advance on the first day of each period. 
    
    When the Commencement Date is not on the first day of a month, an 
    interim Lease Payment, at the daily amount equal to Lease Payment times 
    the number of periods per year divided by 360, from and including the 
    Commencement Date to the end of the month, shall be due and payable 
    upon Lessee's receipt of an invoice from Lessor. 

4.  SECURITY INTEREST 
    -----------------

    Lessee grants to Lessor a security interest in the Software, the 
    Software License, the Software License Agreement, all other rights 
    acquired by Lessee from the Software Licensor relating to the Software, 
    and the Equipment, together with all options, accessories, accessions, 
    and replacements to the Equipment and all proceeds thereof, including 
    insurance proceeds, and all general intangibles related thereto 
    ("Collateral").  The security interest granted by Lessee includes any 
    upgrades, new releases or new versions of the Collateral.

                                                                        Page 1
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5.  LEASE NOT CANCELLABLE; LESSEE'S OBLIGATIONS ABSOLUTE 
    ----------------------------------------------------

    Lessee's obligation to pay shall be absolute and unconditional and 
    shall not be subject to any delay, reduction, set-off, defense, 
    counterclaim or recoupment for any reason whatsoever, including any 
    failure of the Software or Equipment.  If the Software or Equipment is 
    unsatisfactory for any reason, Lessee shall make any claim solely 
    against Software Licensor and Equipment manufacturer or vendor and 
    shall, nevertheless, pay Lessor all amounts payable under the Lease. 
    
6.  TITLE 
    -----

    (a) SOFTWARE.  No title or right in the Software or Software 
    License shall pass to the Lessee by virtue of this Agreement.  All 
    upgrades, new releases or new versions of the Software acquired by 
    Lessee shall immediately become subject to the Lease.

    (b) EQUIPMENT.  The Equipment is and shall remain the property of 
    Lessor. Lessee shall have no right, title or interest in the Equipment, 
    except as set forth in the Lease. The Equipment is and shall remain 
    personal property and shall not become a fixture or realty. Lessee 
    shall affix to the Equipment any labels supplied by Lessor indicating 
    Lessor as the owner.
    
7.  SELECTION AND USE OF SOFTWARE 
    -----------------------------

    Lessee shall be responsible for selection, use, and results 
    obtained from the Software and Equipment and acknowledges that Lessor 
    is not a developer of, dealer in, or licensor of, the Software and that 
    Lessor is not a manufacturer of or dealer in the Equipment.  Lessee 
    authorizes Lessor to insert in each Lease the identifying data of the 
    Software and Equipment. 

8.  ASSIGNMENT OF WARRANTIES 
    ------------------------

    Lessor assigns to Lessee, to the extent assignable, for the term of 
    this Lease, any warranty applicable to the Software and Equipment, and 
    authorizes Lessee to obtain the customary service and support furnished 
    by Software Licensor and Equipment manufacturer or vendor at Lessee's 
    expense.  

9.  DISCLAIMER OF REPRESENTATIONS AND WARRANTIES BY LESSOR 
    ------------------------------------------------------

    LESSOR MAKES NO REPRESENTATION OR WARRANTY, DIRECT OR INDIRECT, 
    EXPRESS OR IMPLIED, WITH RESPECT TO THE SOFTWARE AND EQUIPMENT, 
    INCLUDING THOSE OF THE DURABILITY, SUITABILITY, MERCHANTABILITY, 
    FITNESS FOR PARTICULAR PURPOSE, CONDITION, OR DESIGN.  AS TO LESSOR, 
    LESSEE LEASES THE SOFTWARE AND EQUIPMENT "AS IS".  LESSEE WAIVES ALL 
    RIGHT TO MAKE ANY CLAIM AGAINST LESSOR FOR BREACH OF ANY WARRANTY OF 
    ANY KIND WHATSOEVER.  
    
    LESSOR SHALL NOT BE LIABLE TO LESSEE FOR ANY LOSS, DAMAGE OR 
    EXPENSE OF ANY KIND CAUSED BY OR RELATED TO, DIRECTLY, INDIRECTLY OR 
    CONSEQUEN-TIALLY, THE SOFTWARE AND EQUIPMENT OR FOR ANY CONSEQUENTIAL 
    DAMAGES, ANY LOSS OF PROFITS OR SAVINGS, LOSS OF USE, OR ANY OTHER 
    COMMERCIAL LOSS. 

10. POSSESSION, USE AND OPERATION OF SOFTWARE AND EQUIPMENT 
    -------------------------------------------------------

    (a) DELIVERY AND INSTALLATION.  Lessee shall arrange and pay for
    the delivery and installation of the Software and Equipment. 

    (b) USE AND MAINTENANCE.  Lessee shall use the Software and 
    Equipment in a good and careful manner and in compliance with all 
    operating instructions, laws and regulations and the Software License 
    Agreement. 

                                                                        Page 2

<PAGE>

    (c) ALTERATIONS AND ATTACHMENTS.  Lessee may make alterations, 
    modifications or attachments to the Software and Equipment so long as 
    not in violation of the Software License Agreement.  Any alterations, 
    unless consented to by the Software Licensor, shall not be made to the 
    original Software, but only to a copy.  All alterations, modifications 
    and attachments to the Equipment which cannot be readily removed 
    without damaging the function, use or economic value of the Equipment 
    shall immediately become a part of the Equipment and property of the 
    Lessor.

    (d) SUBLEASE AND RELOCATION. LESSEE MAY NOT SUBLEASE THE SOFTWARE 
    AND EQUIPMENT OR RELOCATE SUCH ITEMS FROM THE STATE IN WHICH THEY WERE 
    INSTALLED, UNLESS CONSENTED TO BY LESSOR.

    (e) ASSIGNMENT BY LESSEE. LESSEE SHALL NOT ASSIGN, TRANSFER OR 
    OTHERWISE DISPOSE OF THE LEASE OR COLLATERAL, OR ANY INTEREST THEREIN, 
    OR CREATE OR PERMIT ANY LIEN OR ENCUMBRANCE THEREON, EXCEPT THOSE 
    CREATED BY LESSOR. LESSEE ACKNOWLEDGES THAT ANY ASSIGNMENT BY LESSEE 
    WOULD MATERIALLY INCREASE THE RISK TO LESSOR.

    (f) INSPECTION.  Lessee shall make the Software, Equipment and any 
    maintenance records available for inspection by Lessor during Lessee's 
    normal business hours. 

11. TAXES AND FEES 
    -------------- 

    Lessee shall pay when due, or reimburse (including taxes on any 
    reimbursement) and indemnify and hold Lessor harmless from and against, 
    all taxes, fees, assessments or other charges of any nature whatsoever 
    (except for any taxes based upon Lessor's net income, unless such net 
    income taxes are in substitution for or release Lessee from any taxes 
    which Lessee would otherwise be obligated to pay under this Section), 
    which may be imposed by any taxing jurisdiction upon or relating to the 
    Software and Equipment.  If Lessee determines that any item of Software 
    or Equipment is not taxable, Lessee shall, prior to the date of 
    commencement of any Lease, provide Lessor with written notice of such 
    determination and the basis for such determination. Should any taxing 
    jurisdiction challenge such determination, Lessee shall indemnify 
    Lessor for all costs (including interest, penalties and attorneys' 
    fees) associated with defending Lessee's determination.  Lessee shall 
    file personal property tax returns including all items of Software or 
    Equipment which may be taxable and pay any taxes which may be due 
    rather than waiting for Lessor to file and pay such taxes and then 
    invoice Lessee for reimbursement.
    
12. END OF LEASE - $0 TERMINATION OPTION AMOUNT
    -------------------------------------------

    Provided an Event of Default has not occurred, the Lease has not 
    been terminated, and all Lessee's obligations under the Lease have been 
    satisfied, all Lessor's right, title and interest in the Software and 
    Equipment shall automatically revert to Lessee at the expiration of the 
    Initial Term of the lease.

13. END OF LEASE - GREATER THAN $0 TERMINATION OPTION AMOUNT
    --------------------------------------------------------

    Provided an Event of Default has not occurred, the Lease has not 
    been terminated, and Lessee desires to retain possession of the 
    Software and Equipment, Lessee shall have the option at the expiration 
    of the Lease upon no less than 60 days' and no more than 120 days' 
    prior irrevocable written notice to Lessor: (a) to retain the Equipment 
    and original and all backup copies of the Software upon payment of the 
    Termination Option Amount specified in the Lease, payment of which 
    shall automatically terminate the Lease, or (b) to extend the Lease for 
    12 months at a monthly Lease Payment equal to the Termination Lease 
    Percentage specified in the Lease multiplied by the Software License 
    Fee and Equipment cost.
    
    If the retention or extension options are not exercised, Lessee 
    shall, pursuant to Lessor's instructions and at Lessee's sole expense, 
    return the Equipment and the original and all backup copies of the 
    Software, including documentation, to Lessor in the same operating 
    order as when received, except for normal wear and tear.  Lessee shall 
    return the Software and Equipment to a location in the continental 
    United States specified by Lessor.
    
    If the retention or extension options are not exercised and the 
    Software and Equipment are not returned, the Lease shall be renewed for 
    one period at a time until the Software and Equipment are returned to 
    Lessor and Lessee shall continue to pay Lease Payments in the original 
    amount set forth in the Lease. 

                                                                        Page 3

<PAGE>

14. EARLY TERMINATION OPTION
    ------------------------

    Provided an Event of Default has not occurred, upon no less than 30 
    days' and no more than 90 days' prior irrevocable written notice to 
    Lessor, Lessee may as of any Lease Payment Date, terminate the Lease 
    upon payment to Lessor an amount equal to (1) the total Lease Payment 
    and other sums due and unpaid under the Lease at the date of payment 
    and (2) Stipulated Loss Value set forth in Exhibit B as of the date of 
    payment.
    

15. RISK OF LOSS 
    ------------

    Lessee shall bear the entire risk of loss, theft, destruction and 
    damage to the Software and Equipment ("Event of Loss") after the 
    Commencement Date.  If an Event of Loss shall occur, Lessee shall 
    immediately notify Lessor and, at the option of Lessor, shall promptly, 
    at Lessee's sole cost:
    (a) place the Software and Equipment in good condition, repair and 
    working order.
    (b) replace the Software and Equipment with like Software and Equipment 
    and grant to Lessor all rights in such Software and Equipment and 
    related Collateral. 

    Lessee appoints Lessor as Lessee's attorney-in-fact to make claim 
    for, receive payment of, and execute and endorse all documents, checks 
    or drafts issued with respect to such loss or damage under any 
    insurance policy relating thereto. 

    If and when Lessor shall have received any insurance proceeds on 
    account of an Event of Loss, and if Lessor, in its reasonable judgment, 
    shall be satisfied that Lessee has properly performed the obligations 
    undertaken by this section, Lessor shall pay over to Lessee out of such 
    proceeds the actual amounts expended by Lessee under Section 15 (a) or (b). 
    
16. INSURANCE 
    ---------

    Lessee shall, at its own expense, obtain on the Software and 
    Equipment all risk property damage insurance in such amounts, against 
    such risks, in such form and with such insurers as shall be reasonably 
    satisfactory to Lessor.  The amount of property damage insurance shall 
    not be less than Stipulated Loss Value. Each insurance policy shall 
    name Lessee as an insured and Lessor and its assignees as an additional 
    insured and loss payee and shall contain a clause requiring the insurer 
    to give Lessor at least 30 days' prior written notice of any alteration 
    or cancellation of such policies. Lessee shall furnish to Lessor a 
    certificate of insurance or other evidence satisfactory to Lessor that 
    such insurance coverage is in effect, provided, however, that Lessor 
    shall be under no duty either to ascertain the existence of or to 
    examine such insurance or to advise Lessee in the event such insurance 
    shall not comply with the requirements hereof. 
    
17. GENERAL INDEMNITY 
    -----------------

    Lessee shall defend, indemnify and hold Lessor, any assignee and 
    any secured party harmless from and against all claims (including 
    claims based on negligence, tort and strict liability ("Claims")), 
    costs, including reasonable attorney's fees, damages and liabilities 
    arising out of or related to the ownership, selection, possession, 
    leasing, renting, operation, control, use, maintenance, delivery, 
    return or other disposition of the Software and Equipment and/or the 
    Collateral or by operation of law, excluding any Claims which result 
    from the gross negligence or willful misconduct of Lessor. 
    
    Lessor may, at its option and at its sole expense, participate in 
    any such action with counsel of its own choice.  Lessee agrees that it 
    shall not settle or compromise any claim, action or proceeding without 
    first obtaining Lessor's prior written consent. 
    
18. REPRESENTATIONS AND WARRANTIES OF LESSEE 
    ---------------------------------------- 

    Lessee represents, warrants and covenants, with the execution of 
    each Lease that, with respect to this Agreement and each Lease:
    (a) this Agreement and each Lease constitute legal, valid and binding 
    agreements of Lessee enforceable in accordance with their respective 
    terms;
    (b) all financial statements furnished to Lessor are true and 
    correct in all material respects and Lessee shall furnish Lessor with 
    its annual independently reviewed financial statements

                                                                        Page 4

<PAGE>

    and such other financial information as Lessor may reasonably request; and
    (c) the Equipment is personal property and will not become a fixture 
    under applicable law.
    (d) that Lessee is the Licensee of the Software under the Software 
    License Agreement. 
    
19. ASSIGNMENT/TRANSFER BY LESSOR
    -----------------------------

    LESSOR MAY SELL OR OTHERWISE TRANSFER ITS INTEREST IN THE LEASE AND 
    THE COLLATERAL IN WHOLE OR IN PART.  LESSEE CONSENTS TO SUCH TRANSFER 
    AND, IF LESSEE IS GIVEN WRITTEN NOTICE OF ANY TRANSFER, IT SHALL 
    PROMPTLY ACKNOWLEDGE RECEIPT IN WRITING. LESSEE ACKNOWLEDGES THAT ANY 
    ASSIGNMENT BY LESSOR WILL NOT MATERIALLY CHANGE THE DUTY OF THE LESSEE. 
    LESSEE SHALL NOT ASSERT AGAINST ANY TRANSFEREE ANY SET-OFF, DEFENSE OR 
    COUNTERCLAIM THAT LESSEE MAY HAVE AGAINST LESSOR (INCLUDING ANY DEFENSE 
    ARISING OUT OF THE INSOLVENCY OR BANKRUPTCY OF LESSOR) OR ANY OTHER 
    PERSON AND UPON NOTICE FROM LESSOR SHALL PAY THE LEASE PAYMENT AND ANY 
    OTHER AMOUNTS DUE UNDER THE LEASE AS DIRECTED. 

    LESSOR'S TRANSFEREE SHALL BE ENTITLED TO ENFORCE THE RIGHTS SO 
    TRANSFERRED, BUT SHALL BE UNDER NO LIABILITY TO LESSEE TO PERFORM ANY 
    OF THE OBLIGATIONS OF LESSOR, THE SOLE REMEDY OF LESSEE BEING AGAINST 
    LESSOR.  LESSOR SHALL NOT BE RELIEVED OF ITS OBLIGATIONS HEREUNDER, 
    EXCEPT AS SPECIFICALLY PROVIDED. 
    
20. LATE PAYMENTS 
    -------------

    If any amount to be paid to Lessor is not received within 5 days 
    after its due date, Lessee shall pay Lessor on demand a late charge of 
    1.5% (or the maximum allowed by law, whichever is less) of such payment 
    for each month, or any part thereof, that the payment is not received. 

21. DEFAULT; NO WAIVER 
    ------------------

    Lessee shall be in default under the Lease upon the occurrence of 
    any of the following event ("Events of Default"):  
    (a) Lessee fails to pay any amount required to be paid under the 
    Lease within 5 days after the due date; 
    (b) Lessee fails to perform any other provisions under the Lease, or any
    other Lease incorporating this Agreement, and such failure shall continue 
    unremedied for a period of 10 days after written notice from Lessor; 
    (c) Any representation or warranty made by Lessee in the Lease or 
    related documents is inaccurate in any material respect; 
    (d) Lessee makes an assignment for the benefit of creditors, consents to 
    the appointment of a trustee or receiver, or if either shall be appointed 
    for Lessee or for a substantial part of its property without its consent; 
    (e) any petition or proceeding is filed by or against Lessee under 
    any Federal or state bankruptcy or insolvency code or similar law; 
    (f) if applicable, Lessee makes a bulk transfer subject to the 
    provisions of the Uniform Commercial Code; 
    (g) Lessee shall default under any other agreement with Lessor or 
    Fleet Bank, N.A. or their successors or assigns; or 
    (h) Lessee suffers an adverse material change in its financial 
    condition from the Commencement Date and Lessor, acting in good faith, 
    deems itself or any of its Collateral to be insecure. 

    Any failure of Lessor to require strict performance by Lessee or any waiver
    by Lessor of any provision in the Lease shall not be construed as a consent
    or waiver of any other breach of the same or of any other provision. 

22. REMEDIES 
    --------

    Upon the occurrence of an Event of Default, Lessor may, in its sole 
    discretion, do any one or more of the following: 
    (a) proceed by appropriate court action to enforce performance by Lessee 
    of the terms of the Lease, or recover from Lessee all damages or expenses,
    including reasonable attorneys' fees, arising from the Event of Default; 
    (b) declare the Lease to be in default; 

                                                                        Page 5

<PAGE>

    (c) terminate the Lease in whole or in part; 
    (d) recover from Lessee all amounts then due and as liquidated 
    damages the Stipulated Loss Value which would have been due on the 
    occurrence of the exercise by Lessee of its Early Termination Option; 
    (e) take possession of and remove Equipment and the original and 
    all backup copies of the Software, wherever located, without demand or 
    notice, without any court order or other process of law, without 
    liability to Lessor or its agents for entry, damage to property or 
    otherwise, except for gross negligence or willful misconduct; 
    (f) demand that Lessee return any or all items of Software and 
    Equipment to Lessor in accordance with Section 13 and, for each day 
    that Lessee fails to return any item of Software and Equipment, Lessor 
    may demand an amount equal to the Lease Payment prorated on the basis 
    of a 30-day month, in effect immediately prior to such default; and
    (g) upon demand by Lessor, Lessee shall immediately cease using the 
    Software and Equipment and remove such Software from any computer on 
    which it is installed. 

    Lessor shall, to the extent permitted by law or any agreement 
    pertaining to the Collateral, sell, lease or otherwise dispose of all 
    or any portion of the repossessed or recovered Collateral in a 
    commercially reasonable manner, with or without notice and on public or 
    private bid.  The cash proceeds from any sale or other disposition, or, 
    if the Collateral is leased, the present value, discounted at 3%, of 
    the Lease Payments due under any replacement lease for a term not to 
    exceed the expiration of the lease or renewal lease (all such amounts 
    being referred to as "Proceeds") shall be retained by Lessor.  If the 
    net proceeds (Proceeds less all costs and expenses, including 
    reasonable attorney's fees, incurred in connection with the recovery, 
    repair or disposition of the Software and Equipment) shall be less than 
    the amount Lessee owes to Lessor, Lessee shall be liable for such 
    deficiency.  Lessor may pursue any other remedy available at law or in 
    equity, including seeking damages, specific performance and injunctive 
    relief. 
    
    No right or remedy is exclusive of any other or permitted by law or 
    equity. All such rights and remedies shall be cumulative and may be 
    enforced concurrently or individually from time to time.  Except as set 
    forth expressly in this Section and to the extent permitted by 
    applicable law, Lessee waives any rights now or hereafter conferred by 
    statute or otherwise which may require Lessor to sell, lease or use the 
    Software and Equipment in mitigation of Lessor's damages or which may 
    otherwise limit or modify any of Lessor's rights or remedies and Lessee 
    waives any rights conferred upon Lessee by UCC Sections 2A-508 through 
    2A-522. 

23. BANKRUPTCY OF SOFTWARE LICENSORS 
    --------------------------------

    The bankruptcy of the Software Licensor or Equipment manufacturer 
    or vendor shall not be a valid cause for Lessee to terminate Lease 
    Payments to Lessor. Lessee shall take all action necessary to protect 
    Lessee's rights to use the Software under Section 365 of the Bankruptcy 
    Code.  Lessee shall elect to retain its rights under the Bankruptcy 
    Code to use the Software, and to the extent the Software License grants 
    customer access to the source code, Lessee shall make written request 
    under the Bankruptcy Code of the Bankruptcy Trustee to obtain the 
    source code.  Lessee shall take other reasonable action to protect its 
    rights to use the Software.  In the event Lessee fails to take the 
    action specified above, Lessee appoints Lessor its Attorney-in-fact, to 
    secure, at Lessor's sole discretion and at Lessee's cost, the right to 
    use the Software for Lessee. 

24. MISCELLANEOUS 

    (a) NOTICES.  Service of all notices under the Lease shall be 
    sufficient if delivered personally or mailed to Lessee at the address 
    above set forth, or to such other address as each party may substitute 
    by notice to the other.  Notice by mail shall be effective when 
    deposited in the United States mail, duly addressed and with postage 
    prepaid. 
    
    (b) ENTIRE AGREEMENT.  The Lease is the complete and exclusive 
    statement of the 

                                                                        Page 6

<PAGE>

    agreement between the parties, superseding all proposals or prior 
    agreements, oral or written, and all other communications between the 
    parties relating to the subject matter. 

    (c) GOVERNING LAW.  This Lease shall be governed by and construed 
    in accordance with the laws of the Commonwealth of Pennsylvania. 

    (d) SEVERABILITY.  If any provision shall be held to be invalid or 
    unenforceable, the validity and enforceability of the remaining 
    provisions shall not in any way be affected or impaired. 

    (e) QUIET ENJOYMENT.  So long as Lessee shall not be in default, 
    Lessor shall not interfere with Lessee's right of quiet enjoyment and 
    use of the Software and Equipment. 

    (f) FURTHER DOCUMENTS.  Lessee shall provide Lessor with such 
    documents as Lessor may reasonably request, including documents 
    relating to preserving the security of Lessor, or financing statements 
    under the Uniform Commercial Code.  Lessor may execute Uniform 
    Commercial Code financing statements for and on behalf of Lessee for 
    the purpose of indicating Lessor's interest in the Collateral. 

    (g) TIME.  Time is of the essence with respect to this Lease.

    (h) COUNTERPARTS.  This Lease may be executed in any number of 
    counterparts, each of which shall be deemed an original, but all such 
    counterparts together shall constitute but one instrument.  No security 
    interest in this Lease or the Collateral or any sums payable hereunder 
    may be created through the transfer or possession of any counterpart 
    other than Counterpart No. 1. 

    (i) SURVIVAL OF OBLIGATION. All agreements, representations, 
    indemnities and warranties contained in this Agreement or any related 
    document shall survive the expiration or other termination of this 
    Agreement. 

    (j) SUCCESSORS.  This Lease shall be binding upon and inure to the 
    benefit of Lessor and Lessee and their respective successors and 
    assigns, unless otherwise expressly provided herein. 

    (k) DISPUTES.  THE PARTIES CONSENT TO THE NON-EXCLUSIVE 
    JURISDICTION OF THE STATE AND FEDERAL COURTS IN PENNSYLVANIA AND 
    VIRGINIA IN CONNECTION WITH ANY DISPUTE UNDER THIS LEASE, AND LESSEE 
    WAIVES ITS RIGHT TO TRIAL BY JURY.



LPI SOFTWARE FUNDING GROUP, INC.           PSINET, INC.
LESSOR                                     LESSEE


By:   /S/ Lawrence N. Bazrod               By:   /S/ Harold S. Wills 
    -------------------------------            -----------------------------

Title:   Vice President                    Title:     C.O.O   
        ---------------------------                -------------------------

Date:   September 18, 1996                 Date:   September 19, 1996     
      -----------------------------              ---------------------------


j:\software\agremnts\psinet.doc


                                                                        Page 7

<PAGE>


Exhibits to the Master Software/Equipment Lease Agreement have been omitted.

The following is a list of the omitted Exhibits which the Company agrees to 
furnish supplementally to the Commission upon request:

       Exhibits:
       --------

                 Exhibit A        Form of Software/Equipment Lease Agreement
                 Exhibit B        Stipulated Loss Value Schedule