A late phase II clinical trial of RP56976 (docetaxel), derived from Taxus baccata was performed to evaluate anti-tumour activity, time to progression and clinical toxicity in patients with advanced or recurrent breast cancer. The patients, between 15 and 80 years old with performance status (PS) of 0-2, received at least two cycles of docetaxel 60 mg m-2 intravenously at 3-4 week intervals. Of the 81 patients enrolled, the 72 eligible for the study were given a total of 327 cycles, with a median of four cycles each. Five patients obtained a complete response (CR) and 27 a partial response (PR); the response rate (RR) was 44.4% (95% confidence interval 32.7-56.6%). A relatively high RR of 9/28 (32.1%) was observed in patients who had received prior chemotherapy involving anthracyclines. The dose-limiting toxicity was grade 3-4 leucocytopenia or neutropenia, found in 78.9% and 85.9% patients respectively. Other severe (grade > 3) toxicities included alopecia (38%), anorexia (18.3%), nausea/vomiting (11.3%), and fatigue (9.9%). Hypersensitivity reactions, oedema and skin toxicity were not severe and were reversible. One therapy-related death occurred 10 days after the initial dose was given. These findings indicate that docetaxel has potent activity against metastatic breast cancer, and that the dose of 60 mg m-2 is safe.