The effects of iv administered piperazinedione were studied in 28 evaluable adult and eight evaluable pediatric patients with advanced cancer. Piperazinedione produced predictable myelosuppression of moderate degree at dosages of 3--3.5 mg/m2/day X 5 days by iv injection. When given in this manner, nausea and vomiting did not occur. Single iv doses of 10--15 mg/m2 produced mild-to-moderate nausea and vomiting and mild myelosuppression. Thrombocytopenia was more severe than leukopenia in both schedules. The drug produced comparable dose-related effects in adults and children. Although no therapeutic response was observed in the adults, a partial remission of 6 months' duration was seen in one child with Hodgkin's disease.