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:    September 1, 2006                  /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:    September 1, 2006                  /s/ Agnes Mullady
     ----------------------                 ------------------------------------
                                            Agnes Mullady, Principal Financial
                                            Officer & Treasurer