The activity of amonafide, a benzisoquinoline-1,3-dione, was assessed in 15 patients with advanced or recurrent sarcoma (11 previously treated). Eligible patients had ECOG performance status 0-2, and acceptable renal, hepatic and bone marrow function. Amonafide 300 mg/m2 was given intravenously over one hour daily on five consecutive days, every 3 weeks. Leukopenia and granulocytopenia were the most common and severe toxicities (grade 3 or 4 toxicity in 20% and 27% of patients, respectively). Local irritation and nausea/vomiting, the most common nonhematologic toxicities, were generally mild. No objective responses were seen, though 2 patients had brief stabilization of disease. Amonafide at this dose and schedule has no activity against advanced, recurrent sarcoma.