We investigated the incidence of the anti-HCV antibody and associated factors in 1,031 surgical patients who had received blood transfusion during or after operation from October 1988 to April 1991, at Kyushu University Hospital. One hundred fifteen patients (11.2%) were anti-HCV positive. Sixty of the 219 patients (27.%) with a history of transfusion were positive, as were 55 of 812 (6.8%) without it. Patients aged under 40 showed a 0.6% positive rate (1 of 175) as did 8.5% (54 of 637) of those 40 and over in the no transfusion history group. Among the 637 patients without transfusion histories and aged over 40, patients with preoperative maximum ALT value over 36 IU. l(-1) had significantly higher positivity (16.0%, 29/181) than those with ALT values less than 35 IU. l(-1) (5.5%, 25/456, P < 0.01). The incidence of anti-HCV antibody in preoperative surgical patients in our hospital is ten times higher than that of donors. Anti-HCV are associated with transfusion, age, and liver dysfunction. Operating room personnel are at high risk because of contact with many HCV carrier patients.