FORM 6-K

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549


                          Report of Foreign Issuer


                       Pursuant to Rule 13a-16 or 15d-16
                    of the Securities Exchange Act of 1934


                           For the month of October


                                 BG Group plc
                         100 Thames Valley Park Drive
                                Reading RG6 1PT
                                    ENGLAND

                   (Address of principal executive offices)


The registrant files annual reports under cover of Form 20-F.  By furnishing
the information contained in this Form the reigistrant is not also furnishing
the information to the Commission pursuant to Rule 12g3-2(b) under the
Securities Exchange Act of 1934.





BG Group plc



2 October 2007.


BG Group plc announces that it has today purchased through JPMorgan Cazenove
Limited 350,000 ordinary shares at a price of 834.0674 pence per share. The
purchased shares will all be held as treasury shares.


Following the above purchase, BG Group plc holds 202,797,743 ordinary shares as
treasury shares. The total number of ordinary shares in issue (excluding shares
held as treasury shares) is 3,367,107,628.





END.
                                 SIGNATURES


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, thereunto duly authorized.


                                BG Group plc


Date: 02 October, 2007                        By: ___Ben Mathews___

                                                     Ben Mathews
                                                     Company Secretary