We have many chances to deal with blood transfusion in the operation room, and it is important for us to pay more attention to prevent hospital infection.We surveyed epidemiologically the prevalence of hepatitis B virus surface antigen (HBV) and hepatitis C virus antibody (HCV) in 34,336 patients operated at Hiroshima Prefectural Hospital from April 1993 through March 2001.The prevalence of HBV seropositivity was 1.8% in total, 1.6% in scheduled, and 2.5% in emergent cases. The prevalence of HCV seropositivity was 7.1% in total, 6.8% in scheduled, and 8.0% in emergent cases. Prevalences of both of them in emergent cases were higher than scheduled. The prevalence of HBV was highest (3.4%) in patients with age of 40's, and the prevalence of HCV increased with age. The prevalences of HBV and HCV were highest (4.5% and 19.0%) in the division of surgery and dialysis-kidney disease center.It is important to carry out standard precautions for all patients to prevent hospital infection. Furthermore, we should pay attention to emergent operative cases and operative cases in dialyzed patients.