Forty-eight patients with advanced breast cancer were treated in a disease-specific phase I trial of doxorubicin and iproplatin combination chemotherapy. The doses of doxorubicin ranged between 30 and 50 mg/m2, and the doses of iproplatin ranged between 150 and 250 mg/m2. Myelosuppression was observed at all levels, but was dose-limiting at the highest level. In addition, nausea, diarrhea and malaise were prominent toxicities. Neither cardiac nor renal toxicity was encountered. Nine of 26 (35%) of previously untreated patients, and 5 of 22 (23%) previously treated patients demonstrated partial or complete responses. Although this combination possesses therapeutic activity, given its toxicities, further evaluation of doxorubicin in combination with iproplatin is not recommended.