OBJECTIVE: To present the long-term outcome of patients with locally advanced or metastatic prostate carcinoma treated by first-line antiandrogen monotherapy. PATIENTS AND METHODS: From 1983 to 1990, 41 patients with advanced prostate carcinoma were treated with flutamide monotherapy until progression or the appearance of toxicity. Twenty-five patients (61%) had T3-T4N0M0 and 16 (39%) T2-4N0-3M1 prostate carcinoma. Consensus criteria were adopted to evaluate the response. Plasma testosterone and sexual function were recorded for the first 3 years. RESULTS: Flutamide was administered for up to 147 months; seven patients (17%) interrupted the treatment because of toxicity. There was an objective response in 17 (41%) patients; 20 (49%) had stable disease while four (10%) progressed. There were objective responses, lasting up to 150 months, in 82% of those with M0 and in 18% with M1 disease (P = 0.05). The median time to progression in patients with an objective response and stable disease was 45 and 16 months, respectively (P < 0.001). Thirty-one patients (76%) died from prostate cancer and 10 (24%) from unrelated diseases. The median survival was 67 and 36 months in patients with an objective response and stable disease, respectively (P < 0.001). There was an improvement in performance status in 85% and reduction in bone pain in 83% of the patients; sexual activity was maintained in 63%. CONCLUSION: Monotherapy with flutamide is well tolerated. Objective responses are more frequent in patients with locally advanced disease. Patients with an objective response within 6 months have a prolonged progression-free and overall survival.