Vinorelbine is a new semisynthetic vinca alkaloid with high activity against breast cancer. In this multicenter clinical study we evaluated the activity and toxicity of vinorelbine as a single agent in 30 advanced breast cancer patients pretreated with anthracycline and/or mitoxantrone (24 with recurrent tumor, 6 with non operable cancers). Vinorelbine was given at a weekly dose of 20 mg/m2 for a minimum of 3 weeks. Treatment was continued until there was disease progression or evidence of serious toxicity. Predominant sites of metastasis were viscera (14 cases), soft tissue (11 cases) and bone (5 cases). A median number of 12 doses of vinorelbine (range 3-34) were administered to each patient. Objective responses were recorded in 11 of them and 15 had minimal responses or stable disease. Four patients showed progression of disease during vinorelbine chemotherapy. The median duration of response was 5 months (2-14). The median survival time was 7 months (2-20+): 9 months for responders and 5 months for those with stable or progressive disease. The most important and dose-limiting toxicity was represented by leukopenia. The compliance of patients was very good and the treatment was well accepted by them all including those with low performance status. In conclusion, this study provides further evidence that a weekly schedule with vinorelbine as a single agent is effective and well-tolerated also in pretreated advanced breast cancer patients.