We evaluated the effect of diabetes mellitus on the prognosis of hepatocellular carcinoma after an elective hepatic resection. Of the 342 patients who underwent a hepatic resection between April 1985 and March 1995, 87 (25.4%) were diabetic. Postoperative morbidity was more common among diabetics than among nondiabetics (36.0% vs. 22.5%, P = .0239). The postoperative survival rate and the cancer-free survival rate were also better in patients without diabetes than in those with diabetes (P = .0333, P = .0149). The results of a multivariate analysis show diabetes mellitus to be an independent and prognostic indicator after a hepatic resection with hepatocellular carcinoma. According to the above findings, diabetes mellitus is thus considered to be a risk factor for prognosis after hepatic resection in patients with hepatocellular carcinoma.