Cis-diamminedichloroplatinum II (CDDP; 52-169 mg/m2) mixed with angiotensin II (1.5-10 micrograms/min) was infused into the hepatic artery in 33 patients with hepatocellular carcinoma. Simultaneously, sodium thiosulfate (10-50 g) was administered intravenously in order to reduce the systemic toxicity of CDDP. Over 50 per cent reduction in tumor size was obtained in 18 patients (55%). Complete response was achieved in 4 patients (12%). Serum alpha-fetoprotein (AFP) levels decreased by more than 75 per cent in 10 of 18 patients in whom the previous AFP level was more than 200 ng/ml. The one year survival rate was estimated at 61 per cent by the Kaplan-Meier method. Alimentary symptoms (nausea, vomiting) were mild or non-existent in nearly 90 per cent of treatments. Peptic ulcer and abdominal pain were manifested in small numbers. Severe changes in the laboratory data were not observed. High dosage arterial infusion of CDDP and angiotensin II and intravenous injection of sodium thiosulfate was well tolerated and gave effective therapy in hepatocellular carcinoma.