Hepatitis B infection was endemic in Italy and household transmission has been considered to be the main mode of HBV spread. Prevalence of HBsAg positive subjects was therefore higher in children than in adults. Serum samples from 500 children (aged 6-15 year) without overt liver disease were tested for HBV serum markers in 1979. Serological evidence of HBV infection was present in 16% of the subjects. To verify a possible decline of HBV infection we designed a seroepidemiological study in school children from the same town. Three classes of age (6 yrs, 10 yrs, 14 yrs) were selected. Children were recruited from those attending primary and secondary schools using a systematic cluster sampling. After parents' informed consent sera were collected in May 1989. All were tested for anti-HBc: anti-HBc + ve sera were then tested for HBsAg and anti-HBs (EIA Abbott Lab., Chicago, Ill. USA). Of the 1635 children one was HBsAg positive and 21 were positive for any HBV marker. Both the prevalence of HBsAg and that of any HBV marker were significantly lower (p less than 0.001) in 1989 when compared to the corresponding age-class of 1979.