A phase II study was conducted to assess the toxicity and response rate of vinorelbine (NavelbineR) combined with epirubicin and fluorouracil (NEF) in metastatic breast cancer. Vinorelbine was delivered at a dose of 25 mg/m2 on days 1 and 8, epirubicin at 60 mg/m2 on day 1 and fluorouracil at 600 mg/m2 on day 1, at 3-week intervals. Forty consecutive ambulant patients with breast cancer with measurable metastases were treated with a total of 310 cycles (median 8) as first-line therapy. The objective response rate was 83% (95% CI 71-95) (6/40 CR 15%, 27140 PR 68%). In 3 patients, CNS metastases were detected during NEF therapy those who had a partial response in their visceral metastases. Median time to progression was 13 months (95% CI 7-19) and estimated median survival time was 32 months. The main dose-limiting adverse effect, grade III-IV haematological toxicity, was reported in 92% of patients. One patient died of neutropenic sepsis. Grade III infections requiring hospitalization were observed in 8 patients (20%). Half of the patients complained of mild constipation, nausea or stomatitis, which were easily managed. Almost all patients had grade III alopecia. One patient with previous adjuvant anthracycline therapy (CEF x 9 two years earlier) developed fatal grade IV cardiac failure associated with pulmonary emboli 2 months after completion of NEF therapy (PR with 6 cycles). In line with the observations of others conducting phase II first-line trials combining vinorelbine and epirubicin, it is concluded that the NEF regimen is effective in metastatic breast cancer. Haematological toxicity, however, requires dose reductions in many patients. Furthermore, careful monitoring of cardiac function is necessary, particularly in patients who received prior adjuvant anthracycline therapy.