Amonafide (benzisoquinolinedione, nafidimide, NSC 308847) is an anticancer agent that functions as a DNA intercalator. Sixteen patients with stage III or IV non-small-cell lung cancer who had not previously received chemotherapy were given amonafide at an initial dose of 300 mg/m2 i.v. daily for 5 days every 21 days. No major objective responses were observed among the 14 patients adequately treated (95% confidence limits 0-20%). Local reactions at the injection site or phlebitis were seen in 14 of the 16 patients. Leukopenia (44%), nausea or vomiting (38%), and thrombocytopenia and rash (each 25%) were also noted. With the low response rate and the toxicity observed, amonafide at this dosage and schedule has limited use in the treatment of non-small-cell lung cancer.