The prevalence of hepatitis B virus markers in the adult Swedish population was investigated according to age, sex, origin and demographic stratum. Sera were collected from 3382 persons in 1990–1. The sera were selected on a statistical basis considered to be representative of the Swedish population from adults aged [les ]18 years. Two of the sera (0·06%) were found to be hepatitis B surface antigen positive. The two hepatitis B carriers were of non-Scandinavian origin as were (8·9%) of those tested. A total of 90 persons had a marker of previous, hepatitis B virus infection, i.e. antibodies against hepatitis B core antigen. Of these, 66 (2·0%) were of Scandinavian origin and 24 (18·1%) from highly endemic areas. The overall hepatitis B virus marker prevalence was 2·7%. The highest age-specific prevalence of hepatitis B markers in those of Scandinavian origin was in those born in 1939 and earlier. In this age-group, women had a significantly higher prevalence (3·6%) than males (1·9%). The lowest prevalence was found in those born in 1970 and later. No significant, age-related differences between younger or older persons, or between men and women, could be found in persons of non-Scandinavian origin. The results showed significant differences in exposure to hepatitis B virus among the indigenous population, compared with those of non-Scandinavian extraction. The results do not support the proposal to include hepatitis B vaccination in the Swedish immunization schedule.