The purpose of this study was to evaluate gemcitabine plus paclitaxel in heavily pretreated patients with metastatic breast cancer (MBC). Patients with MBC with second or third relapse to anthracycline-containing regimens received a 3-hour infusion of paclitaxel 175 mg/m2 on day 1, and gemcitabine 1.0 g/m2 on days 1, 8, and 15, every 28 days. Because of unacceptable thrombocytopenia seen in the first 5 patients, the gemcitabine schedule was changed to days 1 and 8 (G-1,8) for the remainder of the study, every 21 days. Twenty-nine patients (median age, 46 years; range, 32-68 years) received 137 cycles (median: 4 per patient). The regimen was well tolerated. World Health Organization grades III and IV thrombocytopenia were observed in 5 (18.5%) of the first 27 cycles (G-1,8,15), and in 6 (5.4%) of the 110 subsequent cycles (G-1,8)--p = 0.04 for the difference between schedules. Five patients had grade I and two had grade III neuropathy. Eight patients had grade III neutropenia, two had grade IV neutropenia associated with fever (G-1,8,15), and eight had grades I and II myalgia and fatigue. There were 16 (55%) objective responses (95% CI 36-73%); 5 (17%) complete responses, 11 (38%) partial responses (95% CI 3-30% and 19-56%, respectively), and 6 (20.5%) patients with stable disease. Median response duration was 8 months (range, 4-26 months). Median overall survival was 12 months (range, 4-28+ months), and 1-year and 2-year survival rates were 45% and 30%, respectively. This phase II study demonstrated a manageable toxicity profile with the gemcitabine day 1, 8 schedule in combination with paclitaxel and significant and promising activity in heavily pretreated patients with MBC. A confirmatory phase III trial is warranted.