This phase II study combined paclitaxel (Taxol; Bristol Myers Squibb Company, Princeton, NJ) 135 mg/m2 by 3-hour infusion on day 1 and vinorelbine 25 mg/m2 on days 1 and 8 (in the first 14 patients) or on days 1 and 3 (in the subsequent 20 patients). The courses were repeated every 3 weeks. The second vinorelbine dose (on days 3 or 8) was reduced or omitted according to the toxicities encountered. Thirty-four patients have been treated to date; 21 had received one prior regimen of chemotherapy, 11 had two prior regimens, and two had three prior regimens. Only two patients (6%) had not been exposed to anthracyclines. One hundred twenty-six courses have been administered: 52 with vinorelbine given on days 1 and 8, and 74 with vinorelbine administered on days 1 and 3. The most frequent toxicity was grade 4 neutropenia, which occurred in 64% of the courses; 13 episodes of febrile neutropenia have been reported in eight patients. Filgrastim was administered in 43% of the courses because of febrile neutropenia or delayed recovery (72 hours) from grade 4 neutropenia. Mucositis was observed in 18% of the courses (12% grade 1, 3% grade 2, and 3% grade 3). The dose of vinorelbine was reduced or omitted in 86% of courses with the days 1 and 8 schedule, and in 48% of courses with the days 1 and 3 schedule. Among 28 evaluable patients, two complete and 10 partial responses have been observed (response rate, 43%, 95% confidence interval, 19% to 51%). Median duration of response is 5+ months (range, 1 to 15 months). In conclusion, this combination is active and has acceptable toxicities in anthracycline-pretreated breast cancer patients. The delivered dose intensity of vinorelbine is higher with the schedule adopted later in the study, with vinorelbine given on days 1 and 3.