content: <PAGE>
  
                        SECURITIES AND EXCHANGE COMMISSION
  
                              Washington, D.C. 20549
  
                                     FORM 8-K
  
                                  CURRENT REPORT
  
  
  Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
  
  Date of Report (Date of earliest event reported) January 28, 2000.
                                                   ----------------
  
                          CONCENTRIC NETWORK CORPORATION
        -------------------------------------------------------------------
              (Exact name of registrant as specified in its charter)
  
  
                 Delaware                       000-22575           65-0257497
        -----------------------------------------------------------------------
          (State or other jurisdiction         (Commission        (IRS Employer
              of incorporation)               File Number)     Identification No.)
  
  
                 1400 Parkmoor Avenue, San Jose, California 95126
                 ------------------------------------------------
               (Address of principal executive offices)     (Zip Code)
  
  
         Registrant's telephone number, including area code (408) 817-2800
                                                            --------------
  
  
  
                                        N/A
        ------------------------------------------------------------------
           (Former name or former address, if changed since last report)
  <PAGE>
  
       Item 2.  ACQUISITION OR DISPOSITION OF ASSETS
  
       On January 28, 2000 (the "Effective Date"), Concentric Network Corporation
  (the "Registrant"), acquired all of the outstanding capital stock of Internet
  Technology Group ("ITG"), a public liability company organized under the laws of
  Scotland (the "Acquisition"), pursuant to a Scheme of Arrangement (the "Scheme
  of Arrangement") dated September 7, 1999, by and among Registrant and ITG. As a
  result of the Acquisition, ITG became a wholly owned subsidiary of Registrant on
  the Effective Date.
  
       Pursuant to the Scheme of Arrangement and on the Effective Date, Registrant
  paid 71,427,189 British Pounds, which is approximately U.S. $115,354,910 in cash
  and issued 4,728,130 shares of its common stock in consideration for all of the
  issued and outstanding shares of capital stock of ITG.  In addition, the
  Registrant issued an additional 102,500 shares of its common stock as
  consideration for shares of capital stock of ITG issued upon exercise of
  outstanding ITG options at the closing. The Registrant funded the cash
  portion of the consideration from its working capital.
  
       The description contained in this Item 2 of the transactions contemplated
  by the Scheme of Arrangement is qualified in its entirety by reference to the
  full text of the Implementation a copy of which is attached hereto as
  Exhibit 2.1.
  
  Item 7.    FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND
             EXHIBITS
  
       (a)   FINANCIAL STATEMENTS
  
       The Registrant will provide the financial statements required by paragraph
  (a) of Item 7 of Form 8-K promulgated by the Commission pursuant to the
  Securities Exchange Act of 1934, as amended (the "Exchange Act"), if any such
  information is required, within 60 days of the date that this initial report on
  Form 8-K must be filed with the Commission.
  
       (b)   PRO FORMA FINANCIAL INFORMATION
  
       The Registrant will provide the pro forma financial information required by
  paragraph (b) of Item 7 of Form 8-K promulgated by the Commission pursuant to
  the Exchange Act, if any such pro forma financial information is required,
  within 60 days of the date that this initial report on Form 8-K must be filed
  with the Commission.
  
       (c)   EXHIBITS.
  
             2.1   Implementation Agreement dated September 7, 1999.
  
             99.1  Press Release dated January 28, 2000.
  <PAGE>
  
  SIGNATURE
  
  
       Pursuant to the requirements of the Securities Exchange Act of 1934, the
  registrant has duly caused this report to be signed on its behalf by the
  undersigned hereunto duly authorized.
  
                                      CONCENTRIC NETWORK CORPORATION
  
  
                                        /s/ Michael F. Anthofer
                                      --------------------------------------
                                      Michael F. Anthofer
                                      Senior Vice President, Chief Financial
                                      Officer
  
                                      Date: February 14, 2000
  <PAGE>
  
                          CONCENTRIC NETWORK CORPORATION
  
                            Current Report on Form 8-K
  
                                 INDEX TO EXHIBITS
  
  
  Exhibit No.          Description
  ----------           -----------
  
  2.1                 Implementation Agreement dated September 7, 1999.
  
  99.1                Press Release dated January 28, 2000.
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text: SECURITIES AND EXCHANGE COMMISSION
  
                              Washington, D.C. 20549
  
                                     FORM 8-K
  
                                  CURRENT REPORT
  
  Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934
  
  Date of Report (Date of earliest event reported) January 28, 2000.
                                                   ----------------
  
                          CONCENTRIC NETWORK CORPORATION
        -------------------------------------------------------------------
              (Exact name of registrant as specified in its charter)
  
                 Delaware                       000-22575           65-0257497
        -----------------------------------------------------------------------
          (State or other jurisdiction         (Commission        (IRS Employer
              of incorporation)               File Number)     Identification No.)
  
                 1400 Parkmoor Avenue, San Jose, California 95126
                 ------------------------------------------------
               (Address of principal executive offices)     (Zip Code)
  
         Registrant's telephone number, including area code (408) 817-2800
                                                            --------------
  
                                        N/A
        ------------------------------------------------------------------
           (Former name or former address, if changed since last report)
  Item 2.  ACQUISITION OR DISPOSITION OF ASSETS
  
       On January 28, 2000 (the "Effective Date"), Concentric Network Corporation
  (the "Registrant"), acquired all of the outstanding capital stock of Internet
  Technology Group ("ITG"), a public liability company organized under the laws of
  Scotland (the "Acquisition"), pursuant to a Scheme of Arrangement (the "Scheme
  of Arrangement") dated September 7, 1999, by and among Registrant and ITG. As a
  result of the Acquisition, ITG became a wholly owned subsidiary of Registrant on
  the Effective Date.
  
       Pursuant to the Scheme of Arrangement and on the Effective Date, Registrant
  paid 71,427,189 British Pounds, which is approximately U.S. $115,354,910 in cash
  and issued 4,728,130 shares of its common stock in consideration for all of the
  issued and outstanding shares of capital stock of ITG.  In addition, the
  Registrant issued an additional 102,500 shares of its common stock as
  consideration for shares of capital stock of ITG issued upon exercise of
  outstanding ITG options at the closing. The Registrant funded the cash
  portion of the consideration from its working capital.
  
       The description contained in this Item 2 of the transactions contemplated
  by the Scheme of Arrangement is qualified in its entirety by reference to the
  full text of the Implementation a copy of which is attached hereto as
  Exhibit 2.1.
  
  Item 7.    FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND
             EXHIBITS
  
       (a)   FINANCIAL STATEMENTS
  
       The Registrant will provide the financial statements required by paragraph
  (a) of Item 7 of Form 8-K promulgated by the Commission pursuant to the
  Securities Exchange Act of 1934, as amended (the "Exchange Act"), if any such
  information is required, within 60 days of the date that this initial report on
  Form 8-K must be filed with the Commission.
  
       (b)   PRO FORMA FINANCIAL INFORMATION
  
       The Registrant will provide the pro forma financial information required by
  paragraph (b) of Item 7 of Form 8-K promulgated by the Commission pursuant to
  the Exchange Act, if any such pro forma financial information is required,
  within 60 days of the date that this initial report on Form 8-K must be filed
  with the Commission.
  
       (c)   EXHIBITS.
  
             2.1   Implementation Agreement dated September 7, 1999.
  
             99.1  Press Release dated January 28, 2000.
  SIGNATURE
  
       Pursuant to the requirements of the Securities Exchange Act of 1934, the
  registrant has duly caused this report to be signed on its behalf by the
  undersigned hereunto duly authorized.
  
                                      CONCENTRIC NETWORK CORPORATION
  
                                        /s/ Michael F. Anthofer
                                      --------------------------------------
                                      Michael F. Anthofer
                                      Senior Vice President, Chief Financial
                                      Officer
  
                                      Date: February 14, 2000
  CONCENTRIC NETWORK CORPORATION
  
                            Current Report on Form 8-K
  
                                 INDEX TO EXHIBITS
  
  Exhibit No.          Description
  ----------           -----------
  
  2.1                 Implementation Agreement dated September 7, 1999.
  
  99.1                Press Release dated January 28, 2000.