Immune therapy has traditionally had a limited role in the treatment of solid malignancies, outside of renal cancer and melanoma. However, early evidence of the ability to provoke an effective anti-tumor immune response in prostate cancer has led to interest in developing a variety of immune activating strategies in this disease. The first immune therapy to attain success in prolonging survival for metastatic prostate cancer patients is Sipuleucel-T. Rather than utilizing a typical vaccine approach in which antigens and immune activators are injected into the cancer host, sipuleucel-T was developed to stimulate autologous dendritic cells ex vivo, in order to evade the immune suppressive environment created by the cancer. We review the components of the immune system which may be harnessed in the development of immunotherapy in the setting of the recent success with sipuleucel-T.