Twenty-six patients with metastatic breast cancer received cis-dichlorodiammineplatinum(II) either as a single dose of 100 mg/m2 iv every 3--4 weeks or as a continuous 5-day infusion of 20 mg/m2/day at 4-week intervals. Fourteen patients were treated with the single-dose schedule and 12 patients were treated with the continuous 5-day infusion. No significant response was observed with either dose schedule. Aside from a reduction in the frequency and severity of gastrointestinal toxicity with the continuous 5-day infusion, no real difference was seen with regard to renal and hematologic toxicity with either dose schedule.