The aim of this study is to evaluate the risk of infection of non-A, non-B acute hepatitis (NANB-AH) in hospital employees. Among 593 patients with acute viral hepatitis (AVH), hospital employees were 3/147 (2%) in type A, 19/174 (11%) in type B and 21/272 (8%) in non-A, non-B (NANB). All 43 patients were medical staffs such as doctors, nurses and laboratory technicians. Out of 21 patients with NANB hepatitis of hospital employees, 7 were doctors, 14 nurses and 6 laboratory technicians. Eight of them had preceding accidental needlestick exposures. Out of 17,290 employees of our hospital during 18 years, 27 medical persons developed AVH. They were 2 hepatitis A, 10 hepatitis B and 15 hepatitis NANB. No non-medical staff developed AVH. Out of 15 NANB hepatitis patients, 7 had needlestick accidents 4 to 6 weeks before development of the illness, and all donor patients showed liver diseases. During 3 years (1985 to 1987), there were 116 needlestick accidents in our hospital which happened in medical staffs alone, and 50 of them were NANB hepatitis-related accidents. Three ml of human immune serum globulin (ISG) was administered intramuscurally just after accidents to 23 persons but not to 27 persons. NANB hepatitis were developed in 2 doctors who were not treated with ISG. In conclusion, NANB hepatitis occurred in hospital employees especially in medical staffs.