Sixteen patients [13 acute nonlymphocytic leukemia (ANLL), 2 acute lymphocytic leukemia, 1 chronic myelogenous leukemia in a blast crisis; median age, 40 yr; range, 25-78 yr; 9 male, 7 female] received 23 courses of carboplatin given as a bolus on a daily X 5 schedule. Six patients were given 7 courses of carboplatin at 200 mg/m2/day; 3 patients received 5 courses at 250 mg/m2; 9 patients received 11 courses at 300 mg/m2; 2 patients initially treated at 200 mg/m2 were given their 2nd course at 300 mg/m2. Significant hearing loss documented by audiometry occurred in five patients, including three of nine treated at 300 mg/m2. All five had prior or recent exposure to aminoglycoside antibiotics. Three patients developed cancer and acute leukemia group B grade 3 or 4 mucositis, and 18 of 23 courses were complicated by nausea and vomiting. Marrows were hypocellular or aplastic in all patients treated at the highest dose. No complete responses occurred, although two patients with ANLL treated at 300 mg/m2 achieved partial responses lasting 71 and 138 days. The t1/2 alpha [half-life (t1/2)], t1/2 beta, and total body clearance of ultrafilterable platinum were comparable to those previously described by us in patients receiving bolus doses of carboplatin of 22-77 mg/m2/day X 5. Carboplatin has activity in ANLL.