Results of recent clinical trials have intensified interest in immunotherapy for cancer. Among the most promising candidates for immunotherapy are patients with prostate cancer. Results of therapeutic vaccine clinical trials in this population have suggested statistically significant and clinically meaningful improvements in overall survival, with substantially fewer side effects than with chemotherapy. Of particular interest are sipuleucel-T, the first U.S. Food and Drug Administration-approved therapeutic cancer vaccine, and PSA-TRICOM (PROSTVAC), a therapeutic cancer vaccine in phase III testing. The immune checkpoint inhibitor ipilimumab is also stirring considerable interest, with two phase III trials ongoing in prostate cancer. This article highlights data emerging from these trials and addresses remaining questions and practical clinical implications of this therapeutic strategy.