Fifty-five women with metastatic breast cancer were treated with a regimen consisting of paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) 175 mg/m2 administered intravenously over 3 hours on day 1 only plus leucovorin given intravenously over 30 to 60 minutes followed by 5-fluorouracil 350 mg/m2 via intravenous push on days 1 to 3 every 28 days for six cycles. Eight patients were chemotherapy naive. Of 47 previously treated women, 30 had received anthracyclines. Fifty-two patients were evaluable for response. Three (6%) experienced a complete response and 24 (46%) had a partial response, for an overall response rate of 52%. Patients previously exposed to doxorubicin had a response rate similar to those with no prior doxorubicin exposure (50% v 54%, respectively). The median duration of response was 8.6 months and median survival was 17.7 months. Toxicity was modest, with grade 3 or 4 neutropenia observed in only 5.5% (15 of 274) of cycles. Preliminary results indicate that paclitaxel/5-fluorouracillleucovorin is an active, well-tolerated regimen for treating metastatic breast cancer.