The incidence of hepatitis C virus (HCV) antibody positivity is unknown. The purpose of this study was to clarify the prevalence of HCV infection among surgical patients and to identify high risk surgical patients. HCV antibody tests were performed in 789 surgical patients between April 1991 and March 1992. Of these patients, 129 (16.3%) tested positive, which was much higher than the positivity of the ordinary Japanese. Hepatobiliary diseases and portal hypertension were associated with a higher positivity than other disease categories (94 of 206, 45.6% versus 35 of 583, 6%; p < 0.0001). Patients above 50 years of age had a higher positivity than their younger counterparts (118 of 578, 20.4% versus 11 of 211, 5.3%; p < 0.0001). The HCV positivity was as high as 54.1% (119 of 220) among surgical patients with known risk factors for hepatitis, in contrast to only 1.9% (10 of 569) among those without such risk factors. We conclude that surgical patients have a high incidence of HCV infection, for whom medical professionals should pay special attention to avoid disease transmission.