Prostate cancer is the most common malignancy in American men. Metastatic prostate cancer is incurable, with the currently best treatment, androgen ablation, being only palliative. Therefore, there is a need to develop new, more effective therapies against this disease. Multiple immunotherapeutic strategies are being explored for the treatment of prostate cancer, with the hope that such treatment will be more effective and have fewer side effects than current treatment options. Several immunotherapy strategies have been shown to be effective against prostate tumors in animal models, and many of these strategies are beginning to be tested in clinical trials for their efficacy against human prostate cancer. It is likely that effective treatment of prostate cancer will require the use of both immunotherapeutic and traditional approaches in multimodality treatments. In addition, for immunotherapy to be effective against prostate cancer, ways to overcome immune evasion and immunosuppression by the tumor cells will need to be developed.