content: <PAGE>
   
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                         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):
                                 December 16, 1997
  
  
                           CONCENTRIC NETWORK CORPORATION
                               ----------------------
               (Exact name of registrant as specified in its charter)
  
  
             Delaware                     0-22575               65-0257497
  ----------------------------          -----------          ------------------
  (State or other jurisdiction          (Commission           (I.R.S. Employer
        of incorporation)               File Number          Identification No.)
   
  
                              10590 N. Tantau Avenue
                           Cupertino, California  95014
  
                     (Address of Principal Executive Offices)
                                    (Zip Code)
  
        Registrant's telephone number, including area code: (408) 342-2800
  
  
                                  Not Applicable
           ------------------------------------------------------------
           (Former name or former address, if changed since last report)
  
  
  --------------------------------------------------------------------------------
  <PAGE>
   
  This report is filed on behalf of Concentric Network Corporation.
  
  ITEM 5.   OTHER EVENTS.
   
            On December 16, 1997, Concentric Network Corporation announced that it
  has entered into an agreement to sell $150 million Units, each Unit consisting
  of $1,000 in principal amount of  its 12-3/4% Senior Notes due 2007 and a
  Warrant to purchase 6.34072 shares of its Common Stock in a private placement
  within the United States to qualified investors and to certain non-United States
  investors.
  
            The securities to be offered will not be registered under the
  Securities Act of 1933, as  amended (the "Securities Act"), or applicable state
  securities laws, and may not be offered or sold in the United States absent
  registration under the Securities Act and applicable state securities laws or
  available exemptions from registration requirements.
  
  ITEM 7.   EXHIBITS.
  
            (c) Exhibits:
  
                         Exhibit
                         Number
                         ------
  
                         99.1    December 16, 1997 Press Release: Concentric
                                 Network Corporation Prices $150 Million Private
                                 Offering of Units, Consisting of 12-3/4% Senior
                                 Notes Due 2007 and Warrants to Purchase Common
                                 Stock
  
                                        -2-
  <PAGE>
   
                                     SIGNATURES
  
         Pursuant to the requirements of the Securities Exchange Act of 1934, as
  amended, the registrant has duly caused this report to be signed on its behalf
  by the undersigned hereunto duly authorized.
  
  
  Dated: December 30, 1997
                                CONCENTRIC NETWORK CORPORATION
                                ----------------------------------------------- 
                                (Registrant)
  
  
                                By:  /s/  Michael F. Anthofer
                                    -------------------------------------------
                                Name:  Michael F. Anthofer
                                Title: Senior Vice President, Finance and Chief
                                       Financial Officer
  
                                        -3-
  <PAGE>
   
                                   EXHIBIT INDEX
  
                              DESCRIPTION OF DOCUMENT
  
  Exhibit
  Number
  ------
  
    99.1     December 16, 1997 Press Release: Concentric Network Corporation
             Prices $150 Million Private Offering of Units, Consisting of 12-3/4%
             Senior Notes Due 2007 and Warrants to Purchase Common Stock
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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):
                                 December 16, 1997
  
                           CONCENTRIC NETWORK CORPORATION
                               ----------------------
               (Exact name of registrant as specified in its charter)
  
             Delaware                     0-22575               65-0257497
  ----------------------------          -----------          ------------------
  (State or other jurisdiction          (Commission           (I.R.S. Employer
        of incorporation)               File Number          Identification No.)
   
  
                              10590 N. Tantau Avenue
                           Cupertino, California  95014
  
                     (Address of Principal Executive Offices)
                                    (Zip Code)
  
        Registrant's telephone number, including area code: (408) 342-2800
  
                                  Not Applicable
           ------------------------------------------------------------
           (Former name or former address, if changed since last report)
  
  --------------------------------------------------------------------------------
  This report is filed on behalf of Concentric Network Corporation.
  
  ITEM 5.   OTHER EVENTS.
   
            On December 16, 1997, Concentric Network Corporation announced that it
  has entered into an agreement to sell $150 million Units, each Unit consisting
  of $1,000 in principal amount of  its 12-3/4% Senior Notes due 2007 and a
  Warrant to purchase 6.34072 shares of its Common Stock in a private placement
  within the United States to qualified investors and to certain non-United States
  investors.
  
            The securities to be offered will not be registered under the
  Securities Act of 1933, as  amended (the "Securities Act"), or applicable state
  securities laws, and may not be offered or sold in the United States absent
  registration under the Securities Act and applicable state securities laws or
  available exemptions from registration requirements.
  
  ITEM 7.   EXHIBITS.
  
            (c) Exhibits:
  
                         Exhibit
                         Number
                         ------
  
                         99.1    December 16, 1997 Press Release: Concentric
                                 Network Corporation Prices $150 Million Private
                                 Offering of Units, Consisting of 12-3/4% Senior
                                 Notes Due 2007 and Warrants to Purchase Common
                                 Stock
  
                                        -2-
  SIGNATURES
  
         Pursuant to the requirements of the Securities Exchange Act of 1934, as
  amended, the registrant has duly caused this report to be signed on its behalf
  by the undersigned hereunto duly authorized.
  
  Dated: December 30, 1997
                                CONCENTRIC NETWORK CORPORATION
                                ----------------------------------------------- 
                                (Registrant)
  
                                By:  /s/  Michael F. Anthofer
                                    -------------------------------------------
                                Name:  Michael F. Anthofer
                                Title: Senior Vice President, Finance and Chief
                                       Financial Officer
  
                                        -3-
  EXHIBIT INDEX
  
                              DESCRIPTION OF DOCUMENT
  
  Exhibit
  Number
  ------
  
    99.1     December 16, 1997 Press Release: Concentric Network Corporation
             Prices $150 Million Private Offering of Units, Consisting of 12-3/4%
             Senior Notes Due 2007 and Warrants to Purchase Common Stock