A comparison between the 1979, 1982 and 1989 findings indicates that the number of adults susceptible to HAV infections has increased. This fact should be given attention in view of the strongly altered travelling pattern of fairly large sections of the population. It should also be kept in mind that the group of adults born between 1951 and 1960 comprises those adults who have the most frequent contacts with younger children being at the greatest risk of acquiring HAV infection.