Thirty patients with metastatic carcinoma of the breast were treated with a combination of cyclophosphamide, Adriamycin (doxorubicin), and peptichemio (CAP) as an induction regimen, and maintenance regimen consisting of thiotepa, methotrexate, and 5-fluorouracil (TMF). Twenty-four patients were evaluable. Thirteen patients achieved an objective response for a response rate of 54.0% (complete remission plus partial remission). Median duration of response was 9.5 months (0-32+). The CAP regimen had severe myelotoxicity that led to dose reductions in 67% of patients. Furthermore, 50% of the patients required delay (greater than 28-day interval) in chemotherapy courses because of myelosuppression, and peptichemio had to be discontinued in seven patients. The CAP chemotherapy as an induction regimen for metastatic breast carcinoma resulted in underutilization of Adriamycin, and proved to be inferior to other Adriamycin-containing regimens. Although peptichemio used as a single agent had significant activity against breast cancer, it was not suitable for prolonged use in conjunction with other myelosuppressive agents. However, it may have a role in second-line therapy of metastatic breast cancer in conjunction with nonmyelosuppressive agents. The authors were unable to test the efficacy of non-cross-resistant maintenance therapy with TMF in this trial.