In a pilot study a carboplatinu, 250 mg/m2 i.v., and 4-epidoxirubicin, 90 mg/m2 i.v. or mitoxantrone, 10 mg/m2 i.v., combination chemotherapy regimen was studied in a group of breast cancer patients with high-risk metastatic disease. All 11 patients had liver and/or lung metastases. Of the 11 patients, 9 had progressive disease and in 2 patients the disease had stabilised. The toxicity of both anthracycline-containing regimes was similar. Subjective toxicity was mild, but hematological toxicity was inacceptable. The tested carboplatinum-anthracycline combination regimes given in the administered doses are not useful in the treatment of metastatic breast cancer, mainly because of toxicity.