The purpose of this study was to evaluate the antitumor activity of vinorelbine and oral estramustine phosphate in patients with metastatic, hormone-refractory prostate cancer. We evaluated the activity of this association using the following schedule: estramustine phosphate 600 mg/m2/day orally days 1-42 and vinorelbine 25 mg/m2 days 1, 8, 22, 29 cycles repeated every 56 days. Twenty-five patients were included in the study, 24 being evaluable for response and 25 for toxicity. Out of 5 patients with measurable disease, none had an objective response. Of the 24 assessable patients with bone metastases, 9 patients had a > or = 65% decline in pretreatment prostate-specific antigen (PSA) level, stable disease was observed in 10 and 5 patients progressed. Toxicities were minimal. Anemia was observed in 5 patients, alopecia in 4 and nausea and vomiting was observed in 6 patients. Anorexia and weight loss of more than 10% were observed in 2 patients. This combination is active and well tolerated in hormone-resistant prostate cancer. These results support the therapeutic strategy of combining agents that impair microtubule function.