A phase II multicenter clinical study of epirubicin, a new anthracycline anticancer agent, was carried out in 46 patients with advanced breast cancer. The treatment schedule consisted of either 60 mg/m2 every three weeks or 40 to 50 mg/m2 on day 1 and day 8 every four weeks. Objective responses were observed in 23.7% of 38 evaluable patients (1 CR and 8 PR). Response rates according to previous chemotherapy were 50.0% (4/8) in previously non-treated patients and 36.4% (4/11) in patients previously treated with non-anthracyclines. The major adverse effect was bone-marrow suppression; leukopenia was observed in 82.1% of patients, anemia in 53.8% and thrombocytopenia in 20.0%. Other toxicities frequently observed were anorexia (55.0%), nausea-vomiting (55.0%) and alopecia (66.7%), but these seemed to be milder than those produced by doxorubicin.