The relative contribution of various risk factors to the incidence of acute hepatitis B in Italy was estimated using a special surveillance system (SEIEVA) for type-specific acute viral hepatitis. At present 146 health departments (USLs) which contain 21% of the Italian population participate in SEIEVA out of the total of 650. Data on 2460 hepatitis B cases and 708 hepatitis A cases were compared. Hospitalization, surgical intervention, dental therapy, other percutaneous exposures, barber shop shaving, i.v. drug abuse and household contact with HBsAg carriers were associated with acute hepatitis B and a large number of cases were attributable to these risk factors. Because the control programme based on vaccination will not be effective in the short term at reducing hepatitis B incidence, other additional interventions are recommended.