Amonafide, a benzisoquinoline-1,3-dione with anti-tumor activity in preclinical screens, was administered to patients with recurrent or metastatic bidimensionally measurable colorectal cancer. Fourteen patients with no prior chemotherapy for advanced disease, performance status 0-1, and normal bone marrow, renal, and hepatic function were entered. Amonafide 300 mg/m2 was administered intravenously over 1 hour daily for five consecutive days; courses were repeated every three weeks. The major side effect was neutropenia: Grade 3 or 4 toxicity occurred in 5/14 patients. Other toxicities included nausea and vomiting, flulike symptoms, fever, rash and alopecia. Three patients had stable disease, but there were no responses observed. Amonafide at this dose and schedule has no activity in the treatment of colorectal cancer.