OBJECTIVE The study investigated the therapeutic effect of single-agent IV weekly vinorelbine (Navelbine, Pierre Fabre Oncologie, Boulogne, France) a semi-synthetic vinca-alkaloid, in women who had received no prior treatment for advanced or metastatic breast cancer. METHODS Fifty-four patients with assessable advanced or metastatic breast cancer who had received no prior chemotherapy were entered into the study. Fifty patients were evaluable for toxicity and response by WHO criteria; 4 patients were not evaluated because they did not meet the eligibility criteria of the study. Vinorelbine was given as a weekly 30 mg/m2 short IV infusion; and treatment was continued until disease progression or the occurrence of unacceptable toxicity. RESULTS The overall response rate was 50% (complete response 2%, partial response 48%). The response rate according to target was: lymph nodes 64%; liver 28%; lung 66%; local recurrence 60%. The median duration of response was 9 months, the median time to treatment failure was 5 months and the median survival was 15 months. RESULTS Six-hundred thirty cycles were given to 54 patients (53 assessable for tolerance). At least one episode of WHO grade 3/4 granulocytopenia was seen in each of 71% of the patients. Significant nausea/vomiting (WHO grade 3) was seen in less than 1% of cycles and other side effects were uncommon. CONCLUSIONS This study confirms that vinorelbine has major single-agent anti-tumour activity as front-line therapy in advanced breast cancer. Given its excellent tolerance profile and low morbidity, it should be considered for inclusion in first-line combination chemotherapy regimens.