Idarubicin is a new anthracycline derivative with therapeutic efficacy in metastatic breast cancer. In a phase II trial we treated 23 patients with advanced breast carcinoma and favourable prognostic factors. Oral dose of idarubicin was 15 mg/m2 day 1-3 repeated every 3 weeks. All patients were pretreated with hormones. Idarubicin was administered as first line chemotherapy. 20 patients were evaluable for response: 3 patients achieved partial remission, 12 patients stable disease; tumour progression occurred in 5 patients. 3 patients were not evaluable for response because only 1 treatment cycle was administered. Main toxicites were leukopenia (median WHO-grade: 2,r:0-4), nausea and vomiting (median: 1,r:0-4) and alopezia (median: 1,r:0-3). 1 patient died in septic shock: Immediately after the administration of one idarubicine cycle, she was extensively irradiated because of bone metastasis. The fatal course of the disease in this patient does not depend only on the idarubicin therapy, but also on the extensive bone infiltration and on intensive radiation therapy. Idarubicin proved to be an effective drug in metastatic breast cancer with low systemic toxicity and the advantage of oral administration. The drug is an enrichment of therapeutic armament, especially in patients with soft tissue and bone metastasis.