4'Deoxydoxorubicin (25 mg/m2 iv every 3 weeks) was evaluated in 20 patients with advanced breast cancer. The patients had good performance status and had not been heavily pretreated. Although all patients experienced leukopenia, no major therapeutic responses were observed. Nonhematologic toxicity was mild. Further evaluation of 4'-deoxydoxorubicin at this dose and schedule is not warranted in patients with advanced breast cancer.