Exhibit 99.1

                            CERTIFICATION PURSUANT TO
                              U.S.C. SECTION 1350,
                       AS ADOPTED PURSUANT TO SECTION 906
                        OF THE SARBANES-OXLEY ACT OF 2002



     In  connection  with the  Quarterly  Report  of  KeySpan  Corporation  (the
"Corporation")  on Form 10-Q for the period  ending  September 30, 2002 as filed
with the Securities and Exchange  Commission on the date hereof (the  "Report"),
I, Robert B. Catell,  Chairman of the Board and Chief  Executive  Officer of the
Corporation, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002, that:

     (1) The Report fully  complies  with the  requirements  of Section 13(a) or
15(d) of the Securities Exchange of 1934, amended; and

     (2)  The  information  contained  in the  Report  fairly  presents,  in all
material  respects,  the  financial  condition  and results of operations of the
Corporation.








                                      By:    /s/Robert B. Catell
                                      --------------------------
                                      Name:  Robert B. Catell
                                      Title: Chairman of the Board of Directors
                                             and Chief Executive Officer
                                      Date:  November 7, 2002