An epidemiological study was performed in order to evaluate the diffusion pattern and risk factors in an area of hyperendemicity of viral hepatitis in the Neapolitan hinterland. Eight hundred-fifty seven asymptomatic subjects, aged 10 to 65 years, who consecutively went to the public health office of the city of Afragola to ask for a health certificate, were studied. They were interviewed with an epidemiological questionnaire and tested for a basic liver profile and serological markers of both hepatitis A and B viruses. Ninety-five percent of the studied population, had anti-HAV with a prevalence of 73% in the class 10-14 years, and of 98% in the class 45-65 years; 78% had either HBsAg or antibodies anti-HBV (60% in the class 10-14 years and 96% in the class 45-65 years). Healthy carriers state was found in 11.4% of the population and acute asymptomatic type B hepatitis in 3%. For HBV infection the interhuman contact in the family setting appeared to play a major role in viral diffusion. Other favouring factors appeared to be the ingestion of raw shellfish and parenteral therapies with glass syringes not properly sterilized. The data suggest that strategies of prevention of hepatitis diffusion in the Neapolitan area should be based on both reinforcing hygienic measures and the educational level of population and active prophylaxis addressed to people in the very young age.