Sixty-four patients with advanced progressive breast cancer resistant to conventional treatments were entered into the present study. They were randomized to receive either Carminomycin (CMM) 20 mg/m2 or Doxorubicin (DOX) 75 mg/m2, both drugs being administered by i.v. bolus every 3 weeks until progression of the disease. Five patients were not eligible and response could not be evaluated in another eight patients. Three patients had only one course due to disease-related early death. Among twenty-seven evaluable patients who received at least two courses of DOX one complete response and seven partial responses were observed for an overall response rate of 30%. CMM showed significantly lower (P = 0.04) antitumor activity with only one partial response (4%) among the 24 patients who received at least two courses of therapy. Median duration of response dating from the start of chemotherapy was 46 weeks on DOX (range 18-102+) and 30 weeks for the single partial response on CMM. Although the median time to progression for all patients receiving CMM (9 weeks) was significantly shorter (P = 0.04) than for those receiving DOX (30 weeks), patients on DOX had only a marginally longer duration of survival (P = .28) than those initially treated with CMM. Myelotoxicity was more severe in the CMM treated group than in the DOX group. Other toxicities such as alopecia, nausea and vomiting were slightly more severe in the DOX treated group. On the basis of this and other similar randomized studies, CMM cannot be recommended for further application in the treatment of advanced breast cancer.