The sex-specific and age-specific incidence rates of the major parenchymal liver diseases in a North European population were estimated using a computerized registry of all admissions to somatic hospitals in Denmark. The incidence was calculated by counting all incident cases of these diseases reported to the registry in the 5-yr period 1981 to 1985 and dividing the number of cases by the number of person-years at risk in this period. The incidence rates (per million person-years) were for men and women, respectively: infectious hepatitis, 109 and 71; toxic hepatitis, 19 and 22; chronic hepatitis, 27 and 29; alcoholic cirrhosis, 190 and 85; nonalcoholic nonbiliary cirrhosis, 110 and 82; primary biliary cirrhosis, 4 and 14. The pattern of the age-specific incidence rates was similar in men and women in infectious hepatitis, alcoholic cirrhosis, nonalcoholic nonbiliary cirrhosis and primary biliary cirrhosis. Toxic and chronic hepatitis had a higher incidence in women than in men only in older age groups. The incidence of idiopathic hemochromatosis, Wilson's disease, secondary biliary cirrhosis, portal vein thrombosis and Budd-Chiari's syndrome were less than four in both sexes.