<PAGE>

                                                                EXHIBIT 10.1

                            REGISTRATION RIGHTS AGREEMENT                     

     This Registration Rights Agreement (this "Agreement") is made as of the 
19th day of September, 1996 by and between PSINet Inc., a New York 
corporation (the "Company"), and The Chatterjee Management Company, a 
Delaware corporation ("TCG").

                                      WITNESSETH:                     


     WHEREAS, the Company and TCG have entered into a Joint Venture Agreement 
dated as of September 19, 1996 (the "JVA"), pursuant to which, under certain 
circumstances, the Company may issue shares of Common Stock to TCG and/or its 
Affiliates.     

     WHEREAS, it is a condition precedent to the consummation of 
the transactions under the JVA that this Agreement be entered into.     


     WHEREAS, the Company has previously granted registration rights to 
certain other holders of the Company's securities pursuant to the Amended and 
Restated Registration Rights Agreement, the 2/8/95 Registration Rights 
Agreement, the 6/16/95 Registration Rights Agreement and the 7/11/95 
Registration Rights Agreement.     

     WHEREAS, it is the intention of the parties to this Agreement that the 
registration rights granted hereunder shall rank ratably with the 
registration rights under the Amended and Restated Registration Rights 
Agreement, the 2/8/95 Registration Rights Agreement, the 6/16/95 Registration 
Rights Agreement and the 7/11/95 Registration Rights Agreement and with 
registration rights to be granted under other agreements as more fully 
provided in Section 2.7 hereof.     


     WHEREAS, certain defined terms are set forth in Article I hereof.     


     NOW, THEREFORE, for good and valuable consideration, the receipt and 
adequacy of which are hereby acknowledged, and in consideration of the mutual 
covenants contained herein and for other good and available consideration, 
the receipt and adequacy of which are hereby acknowledged, the parties 
hereto, intending to be legally bound, agree as follows:                      
                 







<PAGE>


                                  ARTICLE I

                                  DEFINITIONS 


SECTION 1.1  CERTAIN DEFINITIONS


     As used in this Agreement, the following terms shall have the meanings 
indicated below:     

     "Affiliate" shall have the meaning set forth in the JVA.


     "Amended and Restated Registration Rights Agreement" shall mean the 
Amended and Restated Registration Rights Agreement dated as of January 17, 
1995 among the Company and the other parties thereto, as the same has been 
and hereafter may be amended from time to time to add additional parties 
signatory thereto.     

     "Commission" shall mean the Securities and Exchange Commission or any 
other federal agency at the time administering the Securities Act.

     "Common Stock" shall mean the Common Stock, $.01 par value per share, of 
the Company. 

    "Exchange Act" shall mean the Securities Exchange Act of 1934, as 
amended, and the rules and regulations promulgated thereunder.     

     "Existing Registration Rights" shall have the meaning set forth in 
Section 2.7 hereof.  

   "Holders" shall mean the holders of Registrable Securities then 
outstanding.

     "Other Registration Rights" shall have the meaning set forth 
in Section 2.7 hereof.

     "primary offering" shall have the meaning set forth in Section 2.1 
hereof.

     "Registrable Securities" shall have the meaning set forth in Section 2.4 
hereof.

     "Rule 144A Information" shall have the meaning set forth in Section 4.2 
hereof.

     "secondary offering" shall have the meaning set forth in Section 2.1 
hereof.

     "Securities Act" shall mean the Securities Act of 1933, as amended, and 
the rules and regulations promulgated thereunder.



                                      -2-

<PAGE>

     "2/8/95 Registration Rights Agreement" shall mean the Registration 
Rights Agreement dated as of February 8, 1995 among the Company and the other 
parties thereto, as the same may be amended from time to time.

     "6/16/95 Registration Rights Agreement" shall mean the Registration 
Rights Agreement dated as of June 16, 1995 among the Company and the other 
parties thereto, as the same may be amended from time to time.

     "7/11/95 Registration Rights Agreement" shall mean the Registration 
Rights Agreement dated as of July 11, 1995 among the Company and the other 
parties thereto, as the same may be amended from time to time.      




                                 ARTICLE II                                  

                            REGISTRATION RIGHTS


SECTION 2.1    OPTIONAL REGISTRATIONS


     If at any time or times after the date hereof until the earlier of (a) 
three years after the issuance of the relevant shares of Common Stock to TCG 
or any of its Affiliates pursuant to the JVA (so long as the relevant Holder 
is not an "affiliate" of the Company for purposes of Rule 144 under the 
Securities Act) and (b) September 19, 2003, the Company shall determine to 
register any shares of Common Stock or securities convertible into or 
exchangeable or exercisable for shares of the Common Stock under the 
Securities Act (whether in connection with a public offering of securities by 
the Company (a "primary offering"), a public offering of securities by 
shareholders (a "secondary offering"), or both, but not in connection with a 
registration effected solely to implement an employee benefit plan or a 
transaction to which Rule 145 or any other similar rule of the Commission 
under the Securities Act is applicable), the Company will promptly give 
written notice thereof to the Holders of Registrable Securities then 
outstanding.  In connection with any such registration, if within 30 days 
after their receipt of such notice any one or more of the Holders of 
Registrable Securities request the inclusion of some or all of the 
Registrable Securities owned by them in such registration, the Company will 
notify all of the Holders of its receipt of such request, and, subject to 
Section 2.7 hereof, will use its best efforts to effect the registration 
under the Securities Act of all Registrable Securities which such Holders may 
request in a writing delivered to the Company within 30 days after the notice 
given by the Company with respect to its receipt of such request; provided, 
that such registration is in connection with an underwritten public offering; 
provided, further, that, if the underwriter determines that the registration 
of securities in excess of any amount to be registered by the Company would 
adversely affect such offering then the Company may (subject to the 
allocation priority set forth below) exclude 


                                      -3-


<PAGE>

from such registration and underwriting some or all of the Registrable 
Securities which would otherwise be underwritten pursuant to the notice 
described herein.  The Company shall advise all Holders of Registrable 
Securities promptly after such determination by the underwriter, and the 
number of shares of securities that are entitled to be included in the 
registration and underwriting shall be allocated in the following manner:  
the securities to be sold by the Company shall be included in such 
registration and underwriting, and, subject to Section 2.7 hereof, the number 
of additional shares that may be included in the registration and 
underwriting shall be allocated among all Holders of Registrable Securities 
and all holders of other securities having registration rights granted by the 
Company requesting that Registrable Securities or such other securities, as 
the case may be, be included in such registration and underwriting in 
proportion, as nearly as practicable, to their respective holdings of 
Registrable Securities and such other securities.  All expenses of the 
registration and offering and the reasonable fees and expenses of one 
independent counsel for the Holders and all holders of other securities 
having registration rights granted by the Company shall be borne by the 
Company, except that the Holders and all holders of other securities having 
registration rights granted by the Company shall bear underwriting and 
selling discounts and commissions attributable to their Registrable 
Securities or such other securities, as the case may be, being registered and 
transfer taxes on shares being sold by such Holders or other holders, as the 
case may be.  Without in any way limiting the types of registrations to which 
this Section 2.1 shall apply, in the event that the Company shall effect a 
"shelf registration" under Rule 415 of the Securities Act or any other 
similar rule or regulation, the Company shall take all necessary action, 
including, without limitation, the filing of post-effective amendments, to 
permit the Holders to include their shares in such registration in accordance 
with the terms of this Section 2.1. 

SECTION 2.2   REQUIRED REGISTRATIONS

     Prior to September 30, 2006, one or more of the 
Holders may notify the Company in writing that he, she, it or they (i) intend 
to offer or cause to be offered for public sale all or any portion of his, 
her, its or their Registrable Securities having an aggregate proposed 
offering price of not less than $1,000,000 (such requests shall be in writing 
and shall state the number of shares of Registrable Securities to be disposed 
of and the intended method of disposition of such shares by such Holder or 
Holders) and (ii) request that the Company cause such Registrable Securities 
to be registered under the Securities Act; provided, however, that each 
Holder (or transferee of his, her or its Registrable Securities in accordance 
with the terms of this Agreement) may make only two requests for registration 
under this Section 2.2.  Upon receipt of such notification, subject to 
Section 2.7 hereof, the Company will notify all of the Holders of Registrable 
Securities who would be entitled to notice of a proposed registration 




                                      -4-

<PAGE>

under Section 2.1 above of its receipt of such notification.  Upon the 
written request of any such Holder delivered to the Company within 15 days 
after receipt from the Company of such notification, the Company will use its 
best efforts to cause such of the Registrable Securities as may be requested 
by any Holders (including the Holder or Holders giving the initial notice of 
intent to register hereunder) to be registered under the Securities Act 
within 180 days of the notification by the Holders, in accordance with the 
terms of this Section 2.2; PROVIDED, HOWEVER, that unless such registration 
becomes effective, such registration shall not be counted as Athe one request 
for registration that may be made by each Holder (or transferee of his, her 
or its Registrable Securities in accordance with this Agreement) under this 
Section 2.2.  THE COMPANY SHALL, AFTER CONSULTATION WITH THE HOLDERS 
REQUESTING REGISTRATION,The Holders participating in a registration under 
this Section 2.2 shall select one or more underwriters to sell the 
Registrable Securities to be registered through an underwritten public 
offering.    If the underwriter determines that the registration of 
securities in excess of an amount determined by such underwriter would 
adversely affect such offering, then the Company may (subject to the 
allocation priority set forth below) exclude from such registration and 
underwriting some or all of the Registrable Securities which would otherwise 
be underwritten pursuant to this Section 2.2.  The Company shall advise all 
Holders promptly after such determination by the underwriter, and the number 
of shares of securities that are entitled to be included in the registration 
and underwriting shall be allocated in the following manner:  subject to 
Section 2.7 hereof, the number of shares that may be included in the 
registration and underwriting shall be allocated among all Holders of 
Registrable Securities requesting that Registrable Securities be included in 
such registration and underwriting in proportion, as nearly as practicable, 
to their respective holdings of Registrable Securities.  All expenses of such 
registration and offerings and the reasonable fees and expenses of one 
independent counsel for the Holders shall be borne by the Company; PROVIDED, 
HOWEVER, that (i) the Company shall have no liability for such expenses if 
such registration does not become effective due solely to the action or 
failure to act of any Holder requiring such registration and (ii) the Holders 
shall bear underwriting and selling discounts and commissions attributable to 
their Registrable Securities being registered and transfer taxes on shares 
being sold by such Holders.  The Company may postpone the filing of any 
registration statement required hereunder for a reasonable period of time, 
not to exceed 180 days during any 12 month period, if the Company has been 
advised by legal counsel, which counsel shall be acceptable to the Holders, 
that such filing would require the disclosure of a material transaction or 
other matter which would not otherwise be required to be disclosed at such 
time and the Company determines reasonably and in good faith that such 
disclosure would have a material adverse effect on the Company. 
Notwithstanding anything in this Section 2.2 to the contrary, the Company 
shall not be required to effect a registration under this Section 2.2 more 
than 135 days following the end of the Company's fiscal year, if such 
registration shall require the 

                                      -5-

<PAGE>

preparation of audited financial statements 
for any interim period not otherwise prepared by the Company.  If a demand 
registration is requested during such period, the Company will commence such 
registration promptly following the end of the next fiscal year.  If so 
requested by any Holder in connection with a registration under this Section 
2.2, the Company shall take such steps as are required to register such 
Holder's Registrable Securities for sale on a delayed or continuous basis 
under Rule 415 for a period not to exceed 180 days, and also take such steps, 
during such 180-day period, as are required to keep any registration 
effective until all Registrable Securities registered thereunder are sold.  A 
request under this Section 2.2 shall not be counted as a request under 
Section 2.3. 

SECTION 2.3   FORM S-3

     If the Company becomes eligible to use Form S-3 under the Securities Act 
or a comparable successor form, the Company shall use its reasonable best 
efforts to continue to qualify at all times for registration of its capital 
stock on Form S-3 or such successor form.  Each Holder (or transferee of his, 
her or its Registrable Securities in accordance with the terms of this 
Agreement) shall have the right to request and have effected one registration 
of shares of Registrable Securities on Form S-3 or such successor form for a 
public offering of shares of Registrable Securities having an aggregate 
proposed offering price of not less than $1,000,000 (such request shall be in 
writing and shall state the number of shares of Registrable Securities to be 
disposed of and the intended method of disposition of such shares by such 
Holder or Holders).  The Company shall give notice to all of the Holders of 
the receipt of a request for registration pursuant to this Section 2.3 and 
shall provide a reasonable opportunity for such Holders to participate in 
such a registration.  Subject to the foregoing and the provisions of 
applicable law, the Company will use its best efforts to effect promptly the 
registration of all shares of Registrable Securities on Form S-3 or such 
successor form to the extent requested by the Holder or Holders thereof.  The 
Company shall, after consultation with the Holders requesting registration, 
select one or more underwriters to sell the Registrable Securities to be 
registered through an underwritten public offering. All expenses in 
connection with a registration requested pursuant to this Section 2.3 and the 
reasonable fees and expenses of one independent counsel for the Holders shall 
be borne by the Company; PROVIDED, HOWEVER, that (i) the Company shall have 
no liability for such expenses if such registration does not become effective 
due solely to the action or failure to act of any Holder requiring such 
registration and (ii) the Holders shall bear underwriting and selling 
discounts and commissions attributable to their Registrable Securities being 
registered and transfer taxes on shares being sold by such Holders.  The 
Company may postpone the filing of any registration statement required 
hereunder for a reasonable period of time, not to exceed 180 days, if the 
Company has been advised by legal counsel, which counsel shall be acceptable 

                                      -6-


<PAGE>


to the Holders, that such filing would require the disclosure of a material 
transaction or other factor which would not otherwise be required to be 
disclosed at such time and the Company determines reasonably and in good 
faith that such disclosure would have a material adverse effect on the 
Company with respect to the registration of the Registrable Shares.  At the 
Company's option, the Company may elect to include in such registration on 
Form S-3, securities to be issued by the Company and, if required in order to 
effect the registration of such securities, cause the registration to be made 
pursuant to a Registration Statement on Form S-1 or S-2, which shall count as 
the Registration Statement on Form S-3 to be filed pursuant to this Section 
2.3.  In the event that the Company exercises such option, the inclusion of 
shares by Holders will be subject to the right of the underwriters to reduce, 
in view of market conditions, the number of Registrable Securities proposed 
to be registered (in which case the number of shares of Registrable 
Securities to be registered shall be allocated among all Holders in 
proportion, as nearly as practicable, to their respective holdings of 
Registrable Securities); PROVIDED, HOWEVER, that if the number of Registrable 
Securities pursuant to such a registration shall be reduced to a number which 
is less than 60% of the number of Registrable Securities as to which such 
Holders requested registration pursuant to this Section 2.3 then such 
registration shall not be counted as the Registration Statement on Form S-3 
to be filed pursuant to this Section 2.3 by the Holders requesting such 
registration.  Holders of Registrable Securities will not be permitted to 
require the Company to file a Registration Statement pursuant to this Section 
2.3 more frequently than once every six months.  The registration rights 
provided by this Section 2.3 shall expire on September 19, 2006.  If so 
requested by any Holder in connection with a registration under this Section 
2.3, the Company shall take such steps as are required to register such 
Holder's Registrable Securities for sale on a delayed or continuous basis 
under Rule 415 for a period not to exceed 180 days, and also take such steps, 
during such 180-day period, as are required to keep any registration 
effective until all Registrable Securities registered thereunder are sold. 

SECTION 2.4   REGISTRABLE SECURITIES

     For purposes of this Agreement, the term 
"Registrable Securities" shall mean the Common Stock issued pursuant to the 
JVA and any Common Stock issued or issuable with respect thereto by way of a 
stock dividend or stock split or in connection with a combination of shares, 
recapitalization, merger, consolidation or other reorganization. 

SECTION 2.5   FURTHER OBLIGATIONS OF THE COMPANY

     Whenever the Company is required under this Article II to register any 
Registrable Securities, it agrees that it shall also do the following:




                                      -7-


<PAGE>


          (a)  Use its best efforts to diligently prepare and file with the 
Commission a registration statement and such amendments and supplements to 
said registration statement and the prospectus used in connection therewith 
as may be necessary to keep said registration statement effective (but, in 
the case of a registration under this Agreement, for no more than 180 days 
after the initial effective date of the registration statement) and to comply 
with the provisions of the Securities Act with respect to the sale of 
securities covered by said registration statement for the period necessary to 
complete the proposed public offering;

          (b)  Furnish to each selling Holder such copies of each preliminary 
and final prospectus and such other documents as such Holder may reasonably 
request to facilitate the public offering of his or its Registrable 
Securities;

          (c)  Enter into any reasonable underwriting agreement required by 
the proposed underwriter for the selling Holders, if any;

          (d)  Use its best efforts to register or qualify the securities 
covered by said registration statement under the securities or "blue-sky" 
laws of such jurisdiction as any selling Holder may reasonably request, 
provided that the Company shall not be required to register or qualify the 
securities in any jurisdictions which require it to qualify to do business or 
subject itself to taxation or general service of process therein;          

          (e)  Immediately notify each selling Holder, at any time when a 
prospectus relating to his or its Registrable Securities is required to be 
delivered under the Securities Act, of the happening of any event as a result 
of which such prospectus contains an untrue statement of a material fact or 
omits any material fact necessary to make the statements therein not 
misleading, and, at the request of any such selling Holder, prepare a 
supplement or amendment to such prospectus so that, as thereafter delivered 
to the purchasers of such Registrable Securities, such prospectus will not 
contain any untrue statement of a material fact or omit to state any material 
fact necessary to make the statements therein not misleading;

          (f)  Cause all such Registrable Securities to be listed on or 
included in each securities exchange or quotation system (other than PORTAL) 
on which similar securities issued by the Company are then listed;

          (g)  Otherwise use its best efforts to comply with all applicable 
rules and regulations of the Commission and make generally available to its 
security holders, in each case as soon as practicable, but not later than 30 
days after the close of the period covered thereby, an earnings statement of 
the Company which will satisfy the provisions of Section 11(a) of the 
Securities Act;




                                      -8-


<PAGE>


          (h)  Obtain and furnish to each selling Holder, immediately prior 
to the effectiveness of the registration statement (and, in the case of an 
underwritten offering, at the time of delivery of any Registrable Securities 
sold pursuant thereto), a cold comfort letter from the Company's independent 
public accountants in customary form and covering such matters of the type 
customarily covered by cold comfort letters at the holders of a majority of 
the Registrable Securities being sold reasonably request; and

          (i)  Choose the underwriters, auditors, Company legal counsel and 
financial printer to be engaged by the Company in any such registration. 

SECTION 2.6   TRANSFER OF REGISTRATION RIGHTS

     The registration rights of the Holders under this Agreement may be 
transferred to any transferee of at least 500,000 shares (adjusted 
appropriately for stock splits, stock dividends and the like) of Registrable 
Securities in connection with the transfer of at least 80% of the Registrable 
Securities held by the transferor; PROVIDED, HOWEVER, that (i) the 
registration rights may not be transferred to any transferee reasonably 
deemed by a majority of the Board of Directors to be a direct or indirect 
competitor of the Company and (ii) the Company is given written notice at the 
time of or within a reasonable time after such transfer stating the name and 
address of the transferee and identifying the securities with respect to 
which such registration rights are being transferred; PROVIDED, FURTHER, that 
the transferee assumes the obligations of the transferring Holder under this 
Agreement.  Each such transferee shall be deemed to be a "Holder" for 
purposes of this Agreement.  Notwithstanding the foregoing, transfers by any 
Holder to a partner or shareholder of such Holder shall be without 
restriction as to minimum number or percentage of shares. 

SECTION 2.7   PRIOR AND OTHER REGISTRATION RIGHTS AGREEMENTS

     Notwithstanding any provision hereof to the contrary, the provisions of 
this Article II:  (i) shall rank ratably with the registration rights granted 
under the Amended and Restated Registration Rights Agreement (the "Amended 
Registration Rights") and, to the extent the provisions of this Article II 
conflict or are inconsistent with any such Amended Registration Rights, such 
conflict or inconsistency shall be resolved in a manner which, to the 
greatest extent reasonably feasible, affords the Holders and the holders of 
such Amended Registration Rights, the ratable benefits of this Article II and 
such Amended Registration Rights; (ii) shall rank ratably with the 
registration rights granted under the 2/8/95 Registration Rights Agreement 
(the "2/8/95 Registration Rights") and, to the extent the provisions of this 
Article II conflict or are inconsistent with any such 2/8/95 Registration 
Rights, such conflict or inconsistency shall be resolved in a manner which, 
to the greatest extent reasonably feasible, affords the Holders and the 
holders of the 2/8/95 Registration Rights, the ratable benefits of this 
Article II and such 2/8/95 Registration Rights; (iii) shall rank ratably with 
the registration rights granted under the 6/16/95 Registration Rights 
Agreement (the "6/16/95 Registration Rights") and, to the extent the 
provisions of this Article II conflict or are inconsistent with any such 
6/16/95 Registration Rights, such conflict or inconsistency shall be resolved 
in a manner which, to the greatest extent reasonably 

                                      -9-


<PAGE>

feasible, affords the Holders and the holders of the 6/16/95 
Registration Rights, the ratable benefits of this Article II and such 6/16/95 
Registration Rights; (iv) shall rank ratably with the registration rights 
granted under the 7/11/95 Registration Rights Agreement (the "7/11/95 
Registration Rights") and, to the extent the provisions of this Article II 
conflict or are inconsistent with any such 7/11/95 Registration Rights, such 
conflict or inconsistency shall be resolved in a manner which, to the 
greatest extent reasonably feasible, affords the Holders and the holders of 
the 7/11/95 Registration Rights, the ratable benefits of this Article II and 
such 7/11/95 Registration Rights; and (v) shall rank ratably with the 
registration rights to be granted under any other agreement in connection 
with the original issuance of any other capital stock of the Company (the 
"Other Registration Rights") and, to the extent the provisions of this 
Article II shall conflict with any such Other Registration Rights, such 
conflict shall be resolved in a manner which, to the greatest extent 
reasonably feasible, affords the Holders and the holders of such Other 
Registration Rights, the ratable benefits of the provisions of this Article 
II and such Other Registration Rights.                                      


                              ARTICLE III

                    INDEMNIFICATION AND CONTRIBUTION       


SECTION 3.1    INDEMNIFICATION


     Incident to any registration statement referred to in this Agreement, 
and subject to applicable law, the Company will indemnify and hold harmless 
each underwriter, each Holder of Registrable Securities (including its 
respective partners, directors, officers, employees and agents) so 
registered, and each person who controls any of them within the meaning of 
Section 15 of the Securities Act or Section 20 of the Exchange Act, from and 
against any and all losses, claims, damages, expenses and liabilities, joint 
or several (including any investigation, legal and other expenses incurred in 
connection with, and any amount paid in settlement of, any action, suit or 
proceeding or any claim asserted), to which they, or any of them, may become 
subject under the Securities Act, the Exchange Act or other federal or state 
statutory law or regulation, at common law or otherwise, insofar as such 
losses, claims, damages or liabilities arise out of or are based on (i) any 
untrue statement or alleged untrue statement of a material fact contained in 
such registration statement (including any 

                                     -10-


<PAGE>

related preliminary or definitive prospectus, or any amendment or supplement 
to such registration statement or prospectus), (ii) any omission or alleged 
omission to state in such document a material fact required to be stated in 
it or necessary to make the statements in it not misleading, or (iii) any 
violation by the Company of the Securities Act, any state securities or "blue 
sky" laws or any rule or regulation thereunder in connection with such 
registration; PROVIDED, HOWEVER, that the Company will not be liable to the 
extent that such loss, claim, damage, expense or liability (x) arises from 
and is based on an untrue statement or omission or alleged untrue statement 
or omission made in reliance on and in conformity with information furnished 
in writing to the Company by or on behalf of such underwriter, Holder or 
controlling person expressly for use in such registration statement or (y) 
provided that the Company has theretofore timely prepared all necessary 
prospectus supplements or amendments and provided them to the Holder or its 
representative, arises from the failure of any Holder or underwriter to 
comply with such prospectus delivery requirements as are applicable to it.  
With respect to losses, claims, damages, expenses and liabilities arising out 
of or based upon such untrue statement or omission or alleged untrue 
statement or omission in the information furnished in writing to the Company 
by or on behalf of such Holder expressly for use in such registration 
statement or such failure to comply with such prospectus delivery 
requirements, such Holder, severally and not jointly, will indemnify and hold 
harmless each underwriter, the Company (including its directors, officers, 
employees and agents), each other Holder of Registrable Securities (including 
its respective partners, directors, officers, employees and agents) so 
registered, and each person who controls any of them within the meaning of 
Section 15 of the Securities Act or Section 20 of the Exchange Act, from and 
against any and all losses, claims, damages, expenses and liabilities, joint 
or several, to which they, or any of them, may become subject under the 
Securities Act, the Exchange Act or other federal or state statutory law or 
regulation, at common law or otherwise to the same extent provided in the 
immediately preceding sentence.  In no event, however, shall the liability of 
a Holder for indemnification under this Section 3.1 exceed the proceeds 
received by such Holder from its sale of Registrable Securities under such 
registration statement. 

SECTION 3.2   CONTRIBUTION

     If the indemnification provided for in Section 3.1 above for 
any reason is held by a court of competent jurisdiction to be unavailable to 
an indemnified party in respect of any losses, claims, damages, expenses or 
liabilities referred to therein, then each indemnifying party under this 
Article III, in lieu of indemnifying such indemnified party thereunder, shall 
contribute to the amount paid or payable by such indemnified party as a 
result of such losses, claims, damages, expenses or liabilities in such 
proportion as is appropriate to reflect the relative benefits received by the 





                                     -11-



<PAGE>

Company, the other selling Holders and the underwriters from the offering of 
the Registrable Securities as well as the relative fault of the Company, the 
other selling Holders and the underwriters in connection with the statements 
or omissions which resulted in such losses, claims, damages, expenses or 
liabilities, as well as any other relevant equitable considerations.  The 
relative benefits received by the Company, the selling Holders and the 
underwriters shall be deemed to be in the same respective proportions as the 
net proceeds from the offering (before deducting expenses) received by the 
Company and the selling Holders and the underwriting discount received by the 
underwriters, in each case as set forth in the table on the cover page of the 
applicable prospectus, bear to the aggregate public offering price of the 
Registrable Securities.  The relative fault of the Company, the selling 
Holders and the underwriters shall be determined by reference to, among other 
things, whether the untrue or alleged untrue statement of a material fact or 
the omission or alleged omission to state a material fact relates to 
information supplied by the Company, the selling Holders or the underwriters 
and the parties' relative intent, knowledge, access to information and 
opportunity to correct or prevent such statement or omission.  The Company 
and the Holders agree that it would not be just and equitable if contribution 
pursuant to this Section 3.2 were determined by pro rata or per capita 
allocation or by any other method of allocation which does not take account 
of the equitable considerations referred to in this paragraph.  In no event, 
however, shall a Holder be required to contribute any amount under this 
Section 3.2 in excess of the proceeds received by such Holder from its sale 
of Registrable Securities under such registration statement.  No person found 
guilty of fraudulent misrepresentation (within the meaning of Section 11(f) 
of the Securities Act) shall be entitled to contribution from any person who 
was not guilty of such fraudulent misrepresentation.

     SECTION 3.3    EXPENSES, ETC.

          (a)  The amount paid or payable by an indemnified 
party as a result of the losses, claims, damages and liabilities referred to 
in this Article III shall be deemed to include, subject to the limitations 
set forth above, any legal or other expenses reasonably incurred by such 
indemnified party in connection with investigating or defending any such 
action or claim.  The indemnification and contribution provided for in this 
Article III will remain in full force and effect regardless of any 
investigation made by or on behalf of the indemnified parties or any officer, 
director, employee, agent or controlling person of the indemnified parties.   


       (b)  Notwithstanding the foregoing, to the extent that the provisions 
on indemnification and contribution contained in an underwriting agreement 
entered into in connection with any registration statement referred to in 
this Agreement are in 




                                    -12-



<PAGE>

conflict with the foregoing provisions, the provisions in the underwriting 
agreement shall control.                                  

                               ARTICLE IV

                        RULE 144 AND 144A REPORTING      


SECTION 4.1    RULE 144 REPORTING

     With a view to making available the benefits of certain rules and 
regulations of the Commission which may permit the sale of the Registrable 
Securities to the public without registration, the Company agrees to:  (i) at 
all times make and keep public information available as those terms are 
understood and defined in Rule 144 under the Securities Act (and any 
successor rule to Rule 144); (ii) file with the Commission in a timely manner 
all reports and other documents required of the Company under the Securities 
Act and the Exchange Act; and (iii) furnish to each Holder as promptly as 
possible upon its request a written statement by the Company confirming its 
compliance with the reporting requirements of Rule 144 and of the Securities 
Act and the Exchange Act, a copy of the most recent annual or quarterly 
report of the Company, and any other reports and documents so filed as a 
holder may reasonably request in availing itself of any rule or regulation of 
the Commission allowing a holder to sell any such securities without 
registration. 

SECTION 4.2   RULE 144A INFORMATION

     The Company shall, at all times during which it is neither subject to 
the reporting requirements of Section 13 or 15(d) of the Exchange Act, nor 
exempt from reporting pursuant to Rule 12g3-2(b) under the Exchange Act, 
promptly upon the written request of any Holder, provide in writing to such 
Holder and to any prospective transferee of any of Common Stock of such 
Holder the information concerning the Company described in Rule 144A(d)(4) 
under the Securities Act ("Rule 144A Information").  The Company also shall, 
upon the written request of any Holder, cooperate with and assist such Holder 
or any member of the National Association of Securities Dealers, Inc. PORTAL 
system in applying to designate and thereafter maintain the eligibility of 
the Common Stock for trading through PORTAL.  The Company's obligations under 
this Section 4.2 shall at all times be contingent upon receipt from the 
prospective transferees of Common Stock of a written agreement to take all 
reasonable precautions to safeguard the Rule 144A Information from disclosure 
to anyone other than persons who will assist such transferee in evaluating 
the purchase of Common Stock.                        




                                    -13-


<PAGE>

                                  ARTICLE V

                                   GENERAL       

SECTION 5.1    GRANTING OF RIGHTS AGREEMENTS

     The Company shall not grant any registration rights in respect of any 
shares of capital stock of the Company or other securities of the Company if 
such rights would be superior to the registration rights granted to TCG under 
this Agreement; PROVIDED, HOWEVER, that TCG hereby consents and agrees that 
the Company may (i) amend the Amended and Restated Registration Rights 
Agreement from time to time to add additional parties thereto and/or (ii) 
grant in other agreements to other holders of securities of the Company 
registration rights which rank ratably with the registration rights granted 
hereunder to TCG. 

SECTION 5.2   AMENDMENTS, WAIVERS AND CONSENTS


     For purposes of this Agreement and all agreements, documents and 
instruments executed pursuant hereto, except as otherwise specifically set 
forth herein or therein, no course of dealing between the Company and any 
Holder and no delay on the part of any party hereto in exercising any rights 
hereunder or thereunder shall operate as a waiver of the rights hereof or 
thereof.  No covenant or other provision hereof or thereof may be waived or 
amended other than by a written instrument signed by the party so waiving or 
amending such covenant or other provision.  Any waiver or amendment affected 
in accordance with this Section 5.2 shall be binding upon such Holder and 
each future holder of all such securities and the Company at the time such 
waiver or amendment is effected. 

SECTION 5.3   SURVIVAL OF COVENANTS; ASSIGNABILITY OF RIGHTS

     All covenants and agreements of the Company or TCG made herein shall 
survive until fully discharged.  All covenants and agreements of the Company 
herein shall bind the Company's successors and assigns, whether so expressed 
or not, and, except as otherwise provided in this Agreement, all such 
covenants and agreements shall inure to the benefit of TCG's successors and 
assigns. 

SECTION 5.4   GOVERNING LAW

     This Agreement shall be governed by, and construed and enforced in 
accordance with, the laws of the State of New York without reference to its 
principles of conflicts of law. 



                                     -14-


<PAGE>


SECTION 5.5   HEADINGS

     The headings used in this Agreement have been inserted for reference 
purposes only and shall not control or affect in any manner the meaning or 
interpretation of any provision of this Agreement. 

SECTION 5.6   PRONOUNS

     All pronouns and any variation thereof, shall be deemed to refer to the 
masculine, feminine or neuter, singular or plural, as the identity of the 
person or persons may require. 

SECTION 5.7   NOTICES AND DEMANDS     

Any notice or demand which, by any provision of this Agreement or any 
agreement, document or instrument executed pursuant hereto or thereto, except 
as otherwise provided therein, is required or provided to be given shall be 
deemed to have been sufficiently given or served and received for all 
purposes when delivered or 5 days after being sent by certified or registered 
mail, postage and charges prepaid, return receipt requested, or by express 
delivery providing receipt of delivery, to the following addresses:  if to 
the Company, at 510 Huntmar Park Drive, Herndon, Virginia  22070, or at such 
other address designated by the Company to TCG in writing; if to TCG, at its 
mailing address maintained on the books and records of the Company, or at 
such other address designated by TCG to the Company in writing; and if to an 
assignee of TCG, at its address as designated to the Company in writing. 

SECTION 5.8   SEVERABILITY

     The invalidity or unenforceability of any provision of this Agreement 
shall not affect the validity or enforceability of the remaining provisions 
of this Agreement, and this Agreement shall be construed in all respects as 
if such invalid or unenforceable provision were omitted.  All provisions of 
this Agreement shall be enforced to the full extent permitted by law. 

SECTION 5.9   ENTIRE AGREEMENT

     This Agreement constitutes the entire agreement among the parties 
pertaining to the subject matter hereof and supersedes and cancels all other 
prior agreements, understandings, negotiations and discussions, whether 
written or oral, relating to the subject matter hereof.

                                     -15-


<PAGE>


 SECTION 5.10  COUNTERPARTS

     This Agreement may be executed in one or more counterparts, each of 
which shall be deemed to be an original, and all of which together shall be 
deemed one and the same instrument.     















































                                    -16-


<PAGE>

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

                                        PSINET INC.

                                        By:  /S/ WILLIAM L. SCHRADER
                                            ------------------------

                                        Name:   William L. Schrader
                                        Title:  President & CEO 



Accepted and Agreed as of the date first above written.

THE CHATTERJEE MANAGEMENT COMPANY

By:   /S/ W. JAMES PEET
     --------------------
Name:   W. James Peet 
Title:  Vice President
























                                     -17-