In order to determine the frequency of hepatitis A in children and adolescents in the cities of Lima, Arequipa, Piura, Cajamarca and Iquitos, a descriptive cross-sectional study which measured serum anti-hepatitis A antibodies from 1,721 children and adolescents aged 1-15 years was performed. The overall frequency of positive serology was 50.5% (95% CI: 48.1 to 52.9), with lower rates for Lima at 37.4% (95% CI: 35.1 to 39.8) and higher rates for Iquitos at 68.7% (95% CI: 63.6 to 73.4). Seropositivity was higher in the group of 10-15 year-olds with 66.1% and in the socioeconomic status group E with 64.6%. We concluded that the cities studied have a pattern of intermediate endemicity. The frequency of hepatitis A was greater in children and adolescents of lower socioeconomic status and older age.