A vaccine formulation consisting of recombinant vaccinia virus encoding prostate specific antigen (PSA) and recombinant vaccinia virus encoding three co-stimulatory molecule transgenes B7.1, ICAM-1, and LFA-3 (TRICOM). Vaccination with PSA in combination with TRICOM may enhance antigen presentation, resulting in the augmentation of a cytotoxic T cell (CTL) immune response against tumor cells expressing PSA.