The purpose of this randomized, prospective study was to determine whether the infusion of branched-chain amino acid (BCAA)-enriched solution had a preventive effect for treating postoperative hepatic encephalopathy in patients with cirrhosis. Among the 56 patients with cirrhosis, 29 were given BCAA-enriched solution, and 27 were given the conventional amino acid solution for 14 days postoperatively. These groups were indistinguishable with regard to clinical and laboratory criteria at entry, except by sex. The molar ratio of BCAA to aromatic amino acids in the BCAA group was increased postoperatively, whereas the ratio in the control group was decreased, the difference being statistically significant. Among the 29 who received BCAA, three (10.3%) had hepatic encephalopathy; two died and one recovered. Of the 27 control patients, hepatic encephalopathy occurred in three (11.1%); one died and two recovered. There was no significant difference in rate of occurrence of hepatic encephalopathy between the groups. Thus the infusion of BCAA-enriched solution apparently had no preventive effect with regard to hepatic encephalopathy for patients with cirrhosis who underwent surgical treatment.