Between 1968 and 1975 146 patients were admitted to the Würzburg University Hospital for Children because of acute viral hepatitis. 123 (85%) turned out to be HBsAg negative (hepatitis non-B), and 23 (15%) HBsAg-positive (hepatitis B), when tested by solid-phase radioimmunoassay. Subtyping HBsAg revealed a trend from subtype D- towards subtype Y-infections. Analyzed retrospectively, 23 of the non-B and 6 of the B patients apparently had contracted their infection from family or household contacts. Amongst the hepatitis non-B patients, another 16 had contacts at school or nursery school, and 12 had spent their holidays in mediterranian countries. In any type of hepatitis 8 patients previously had been in hospital; in 4 of the 8 non-B cases hepatitis type non-A-non-B is discussed. All the persons who were the suspected source of infection for hepatitis non-B seemed to have suffered from acute hepatitis, while in hepatitis B the only two who could be traced, appeared to be chronically infected. In the Würzburg area, hepatitis non-B, most likely A predominated during infancy whilst adults mostly suffered from hepatitis B. These differences are discussed.