The etiological and clinical aspects of viral hepatitis were evaluated by a retrospective survey of patients hospitalized in 1972, 1973 and 1974 in 12 specialized medical centers scattered throughout Italy. The data refer to 2788 patients suffering from acute viral hepatitis who were hospitalized during the initial 10 days of jaundice. The majority of patients (90%) had not been treated with steroids. For each case, the clinical and biochemical data were recorded, coded, computerized and statistically analyzed. In our patient population viral hepatitis was more frequent among younger patients. We observed a high frequency of HBsAg positive hepatitis (40.7%) which was seldom associated to a history of parenteral exposure and showed an irregular geographical distribution. HBsAg positive hepatitis was similarly distributed between males and females. It was more frequent in patients older than 30 (60%) than in children (18-23%) and younger patients (42%). In our series, the frequency of HBsAg hepatitis found in surgeons (81.8%) and nursing personnel (66.3%), but not in physicians (41.2%), was greater than that of the entire sample due to their exposure to blood.