Serum samples from people born between the years 1895 and 1970 were collected and tested for antibody to hepatitis B surface antigen (anti-HBs) by passive haemagglutination (PHA) and radioimmunoassay (RIA), and for antibody to hepatitis B core antigen (anti-HBc) by immunoelectroosmophoresis (IEOP). Neither anti-HBs nor anti-HBc was detected in the serum from anyone under 15 years of age. The prevalence of anti-HBs and anti-HBc showed peaks of 9.2 and 8.3 per cent, respectively, in the age group of 40-49 years. The distribution of antibody was equal between men and women. Eighty per cent of the sera with anti-HBs were also positive for anti-HBc. All sera positive for anti-HBc also contained anti-HBs.