Recent insights into cell-mediated immunotherapy have led to a wave of new trials involving immunotherapy for prostate cancer. Vaccines have evolved from nonspecific immune stimulants like Bacillus Calmette-Guerin (BCG) to much more specific and potent strategies. Techniques currently being investigated include passive immunotherapy with monoclonal antibodies, adoptive transfer of activated effector T cells, and active immunotherapy involving immunization with whole-cell or antigen-specific vaccines. These therapies are being modified with cytokines and other immune modulating agents. Understanding the mechanisms of antitumor immunity and identifying relevant tumor-specific antigens will likely improve these vaccine strategies and provide them with a niche in the future of prostate cancer therapy.