In 1990, the prevalence of antibodies to hepatitis A virus infection (anti-HAV) was assayed by the ELISA method on a national sample of 1000 recruits aged 18-24 years. The overall prevalence was 29.4% (22.4% in the northern and central regions, 32.2% in the south and islands; p < 0.01). Compared with a similar study conducted in 1981, the results show a marked reduction in anti-HAV prevalence (from 66.3% to 29.4%; p < 0.01). These findings reflect the improved sanitation standards in Italy and indicate that the proportion of non-immune adults is increasing, with a higher risk of symptomatic infection in the near future.