Results from our previous phase II study demonstrating high efficacy and low toxicity for a weekly schedule of 5-fluorouracil (5-FU)/leucovorin in intensively pretreated patients with metastatic breast cancer prompted addition of paclitaxel and cisplatin to this regimen for a phase II study of outpatient first-line treatment of metastatic breast cancer. (MBC). Twenty-eight patients with metastatic breast cancer have been evaluated. Pretreatment comprised adjuvant CTX in 24 out of 28 patients, but no prior CTX for MBC. Patients were treated with 5-FU 2 g/m2 (24 h infusion) plus leucovorin 500 mg/m2 (2 h infusion prior to 5-FU) weekly for 6 weeks (days 1, 8, 15, 22, 29 and 36); in addition, paclitaxel 175 mg/m2 (3 h infusion) was administered on days 0 and 21, and cisplatin 50 mg/m2 (1 h infusion) on days 1 and 22 prior to 5-FU/leucovorin, repeated every 50 days. All patients were treated as outpatients using Port-a-Cath systems and portable pumps. Aside from common total alopecia, neutropenia was common but only of short duration. No episodes of febrile neutropenia occurred. Non-hematologic toxicities (NCl CTC grade, percent of patients) consisted of mild to moderate diarrhea (2+3, 47%), mucositis (2, 14%), and nausea and vomiting (2+3, 60%). Out of 28 patients with bidimensionally measurable disease 25% (seven out of 28) achieved a CR, 57% (16 out of 28) achieved a PR, 11% (three out of 28) had a SD and 7% (two out of 28) had a PD. Overall RR was 82% (95% confidence interval 66-100%). Median remission duration was 8 months, median time to progression 9 months and median survival time 28 months with a median follow-up of 21 months. We conclude that the combination of paclitaxel, cisplatin and 5-FU/leucovorin is an effective non-anthracycline-containing regimen for the first-line treatment of MBC.