Between March 1986 and March 1987, 48 patients with stage D prostate carcinoma were entered into a multicentric pilot study using the pure nonsteroidal antiandrogen nilutamide (Anandron--RU 23908) at the dose of 100 mg t.i.d. as the only therapy until disease progression or the occurrence of toxicity. Minimum follow-up was 15 months. Median age of patients was 72 (56 to 83) and median initial Performance Status (PS) was 1 (0 to 3). Of the 48 patients, 29 were untreated, while 19 patients were progressing following treatment by orchiectomy, LHRH analogs, or other endocrine therapies. According to the National Prostatic Cancer Project (NPCP) criteria, 43 patients were evaluable for response. Overall best response in untreated patients was partial response (PR), 41.6%; stationary disease (SD), 54.1%; 73.6% of pretreated patients achieved SD. Median progression-free survival and overall survival in untreated patients were 325 and 696 days, respectively, and 174 and 447 days, respectively, in pretreated patients. The more common side effects were G.I. toxicity (65%), hemeralopia (27%), and alcohol intolerance (6.2%). Results of this study suggest that Anandron may be a safe and effective treatment for patients with advanced prostatic cancer.