On the basis of results obtained with oral idarubicin administration in breast cancer, which have shown an established antitumor activity in approximately 28% of cases, this compound was combined with cyclophosphamide (also given orally) in postmenopausal patients with an unknown or negative steroid receptor status. The study comprised 45 untreated patients out of which 44 were evaluable for response and toxicity. The mean age was 62.5 years (range 51–75). The majority of patients had soft tissue (24) and visceral organ (17) metastases. Idarubicin was administered in one oral daily dose of 45 mg/m2 on day 1; the oral cyclophosphamide dose was 200 mg/m2 daily on days 3, 4, 5 and 6. An objective response to treatment was observed in 41 % of patients (18/44, 95% confidence interval 28–56%). Complete remission (lung) was observed in 2 patients (5%), while 16 patients achieved a partial response. Eleven patients showed no change, while 15 patients progressed. A particularly good response was obtained in soft tissue metastases (54%, 13/24) while in visceral organs a response was achieved in 31% of patients (5/16). The remissions lasted 2–14 months (median 7 months), and median survival was 14+ months. Toxicity was mild and the treatment well tolerated. Grade I/II leukopenia was observed in 24% of patients (median WBC nadir 3,100); there were no signs of cardiotoxicity. Grade I and II alopecia was observed in 75% of patients; nausea/vomiting were present in 73% of cases. The results of this study indicate that oral administration of idarubicin and cyclophosphamide produces a valuable antitumorigenic effect in postmenopausal breast cancer patients, particularly in soft tissue metastases. Further randomized studies will be needed to evaluate this treatment app