A sero-epidemiological survey of hepatitis B virus (HBV) infection in a randomly selected sample of 957 persons from the population of the Austral Island group in French Polynesia was conducted as a first step before developing an immunization programme strategy. Prevalence rates of HBsAg ranged from 3.09% to 27% in the different islands of the group with a weighted mean of 10.48%, while the prevalence rate for at least one marker ranged from 46.91% to 81.03% with a weighted mean of 64.12%. In the 0-11 months and 1-4 years age groups, 2.08% and 10.57%, respectively, of the children were HBsAg carriers. These findings, when compared to the mean population carrier rate of 10.48%, suggest that HBV transmission occurred mostly after the first year of life. The highest prevalence rate for HBeAg positivity was in the 5-19 years age group (more than 40% of the HBsAg carriers were HBeAg positive), suggesting that contagiousness was greatest in childhood and adolescence. HBsAg was found in 11.45% of women of child-bearing age and HBeAg in 19.09% of women positive for HBsAg. It is concluded that immunization of newborns and infants, using vaccine alone, should be the most effective strategy for reducing HBV infection in the Austral Islands archipelago.