CERTIFICATION PURSUANT TO RULE 30A-2(B) UNDER THE 1940 ACT AND
                     SECTION 906 OF THE SARBANES-OXLEY ACT

I, Bruce N.  Alpert,  Principal  Executive  Officer  of  The GAMCO  Growth  Fund
(the "Registrant"), certify that:

     1.  The Form N-CSR of the Registrant (the "Report") fully complies with the
         requirements  of Section 13(a) or 15(d) of the Securities  Exchange Act
         of 1934, as amended; and

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


Date:    03/01/2007                /s/ Bruce N. Alpert
     -------------------           ---------------------------------------------
                                   Bruce N. Alpert, Principal Executive Officer



I, Agnes Mullady,  Principal  Financial  Officer & Treasurer of The GAMCO Growth
Fund (the "Registrant"), certify that:

     1.  The Form N-CSR of the Registrant (the "Report") fully complies with the
         requirements  of Section 13(a) or 15(d) of the Securities  Exchange Act
         of 1934, as amended; and

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


Date:    03/01/2007                  /s/ Agnes Mullady
     --------------------            -------------------------------------------
                                     Agnes Mullady,
                                     Principal Financial Officer & Treasurer