To assess the prevalence of current or previous infection with viral hepatitis agents in an older nursing home population. A prospective cohort study. Three nursing homes in the greater St. Louis area affiliated with Saint Louis University. Older residents admitted to these facilities. Residents were interviewed and examined for evidence of hepatitis or liver disease. Serum samples were tested for hepatitis B surface antigen (HBsAg), antibody to hepatitis B core and surface antigens (anti-HBc and anti-HBs), antibody to hepatitis A virus (anti-HAV), antibody to hepatitis C virus (anti-HCV), and hepatitis G virus RNA (HGV RNA). Of 329 residents queried, 199 gave consent and were able to participate. The seroprevalence of hepatitis was: HBsAg 0%, anti-HBc 24.1%, anti-HBs 19.5%, anti-HAV 79.9%, anti-HCV 4.5%, and HGV-RNA 10.6%. Frequency of HAV infection increased significantly with age whereas HBV infection correlated with ethnic status and former occupation as a manual worker. A history of blood transfusion was associated with a higher rate of anti-HCV. End stage renal disease, present in 17 patients, was associated with anti-HBc, anti-HCV, and HGV RNA positivity but not with anti-HBs or anti-HAV positivity The seroprevalence of anti-HCV was surprisingly high in this population residing in skilled nursing facilities, and we recommend that all new patients admitted to this type of institution be screened for anti-HCV. The prevalence of HGV RNA was higher than in the general US blood donor population, but the significance of this finding remains uncertain.