Epidemiological data indicate that endemic hepatitis in Greenland is immunologically different from hepatitis type A occurring in large epidemics. The endemic type is characterized by sporadicity, a high incidence in urban areas, and predominance of adult cases indicative of a hepatitis B virus (HBV) etiology. The distribution of hepatitis B surface antigen (HBS Ag) in the healthy population suggests the existence of a hyperendemicity of HBV in some rural areas showing few overt hepatitis cases but a HBS Ag carrier rate up to 25 per cent.