Using RIA and ELISA methods the authors examined HBsAg, anti-HBc IgM and anti-HAV IgM antibodies in 830 adult patients and 101 children with acute viral hepatitis from the catchment area of the South Moravian region. In these groups also the most frequent hepatotropic infectious agent as the possible cause of hepatitis was examined. It was revealed that in adults viral hepatitis A accounted for 22%, viral hepatitis B for 48.5%, viral hepatitis non-A, non-B for 28.8% of the group. The percentage distribution of viral hepatitis in children is different: hepatitis A predominates (65%), hepatitis B is less frequent (22%) and viral hepatitis non-A, non-B is least frequent (13%). It was demonstrated that viral hepatitis non-A, non-B is under our conditions a very frequent disease, it accounts for one quarter of all cases of viral hepatitis and if we take into account that non-A, non-B hepatitis has frequently permanent serious sequelae, then proper attention must be paid to this disease. The authors demonstrate that differentiation of types of viral hepatitis by routine methods is possible which leads to a substantially more accurate differentiation of hepatitis.