PURPOSE: Complete androgen blockade (CAB) does not prolong overall survival (OS) in patients with castration refractory prostate cancer (CRPC). Although there is variable clinical benefit with second-line hormone manipulation, we do not know which patients might benefit the most. OBJECTIVES: To identify clinical predictors of benefit of complete androgen blockade. MATERIALS AND METHODS: We reviewed the records for 54 patients who received treatment with CAB in the setting of disease progression despite castration. We evaluated progression-free survival (PFS) and OS according to PSA at diagnosis, Gleason scores, age, testosterone level, and duration of prior disease control during castration in first line treatment. RESULTS: Among 54 patients who received CAB, the median PFS was 9 months (CI 4.3-13.7) and OS was 36 months (CI 24-48). We did not find an effect of PSA at diagnosis (p = 0.32), Gleason score (p = 0.91), age (p = 0.69) or disease control during castration (p = 0.87) on PFS or OS. Thirty-four patients subsequently received chemotherapy, with a mean OS of 21 months (CI 16.4-25.5, median not reached). CONCLUSION: Age, Gleason score, PSA at diagnosis and length of disease control with castration did not affect PFS or OS. In the absence of predictors of benefit, CAB should still be considered in CRPC.