Amonafide (benzisoquinolinedione; NSC 308847) was subjected to a Phase II trial for the treatment of advanced hormone-refractory carcinoma of the prostate. In addition to adequate baseline organ functions, patients were required to have a favorable performance status, bidimensionally measurable disease and no prior chemotherapy. Amonafide was given at a dose of 225 mg/m2 intravenously daily for 5 days. Treatment cycles were repeated every 21 days. Dose escalation and reduction schema were used based upon toxicities from preceding cycles. Of 47 patients enrolled, 43 were evaluable. The most common toxicities were hematologic to include leukopenia (72%), granulocytopenia (32.6%), and thrombocytopenia (44.2%). There were no complete responses and only 5 partial responses for an overall response rate of 12% (95% confidence interval: 4-25%). The results indicate that Amonafide, in the dose and schedule tested, lacks sufficient activity against hormone-refractory prostate cancer to warrant further trials.