Background: Because prostate cancer is incurable when metastatic and conventional therapies do not offer a clear survival benefit, new therapeutic strategies are warranted. This study is based on the premise that clinically effective cell mediated immune responses against prostate tumors can be elicited by activation of tumor associated antigen specific T cells. Work performed by others and our group suggests that PSA, a protein expressed in virtually all prostate cancers, can serve as a widely expressed candidate antigen for prostate cancer immunotherapy. In particular, we have shown that cultured dendritic cells transfected with mRNA encoding PSA are remarkably effective in stimulating antigen specific immunity in vitro. Therefore, we hypothesize that administration of PSA RNA transfected DC will lead to detectable levels of PSA specific CTL in the peripheral blood of patients with PSA expressing metastatic prostate cancer. It is hoped that these T cell responses also have clinical antitumor activity.