Sipuleucel-T is an immunotherapy indicated for the treatment of metastatic prostate cancer. It offers a new mechanism to treat prostate cancer without the side effects of hormone therapies and chemotherapies. In previous studies sipuleucel-T did not delay disease progression, but demonstrated an overall survival benefit compared to placebo. While clinical trials have evaluated the effects of sipuleucel-T on overall survival and progression, more studies are needed to evaluate its effectiveness and role in the management of prostate cancer. The objective of this study is to identify the incidence and possible predictors for disease progression in patients receiving sipuleucel-T. A retrospective review of patients who received sipuleucel-T between 1 September 2010 and 11 October 2011 was conducted (n = 36). Patients who changed therapy or died within 120 days were classified as experiencing rapid progression. Potential predictors of rapid progression were examined using logistic regression. Seven patients met criteria for rapid progression. Progression occurred in 72.2% of all patients. The median days to progression was 158. No significant predictors of rapid progression were identified. Currently no predictors have been found to be associated with rapid progression in prostate cancer patients on sipuleucel-T.