A recent increased incidence of hepatitis A in the hemophilia populations of Italy, Germany, Belgium and Ireland was studied. The first well-documented outbreak occurred in Italy, where 51 patients with severe hemophilia contracted hepatitis A between the years 1989 and 1992. A case-control study by Mannucci et al. of the first 29 consecutive cases of hemophilia patients with jaundice led to the conclusion that hepatitis A was transmitted to Italian hemophilia patients by solvent-detergent-treated, ion-exchange-purified concentrate. In a retrospective serologic study of the German epidemic, Brakmann et al. isolated 18 seroconversions in a study group of 195 hemophilia patients over a 5-year period. Although several types of concentrate were used in Germany during this time, all but 1 infected patient received large doses of solvent-detergent, ion-exchange product. It was revealed that the 1 exception had a brother with hemophilia who had received solvent-detergent-prepared concentrate and had developed hepatitis A. Transmission to the study patient was therefore attributed to household contact. The Belgian experience corroborated the findings of the Italian and German investigators: several batches of factor VIII, prepared from plasma of Belgian donors in Lille, France, and Vienna, Austria, appeared to be associated with hepatitis A infection, mainly in hemophilia patients who had received large infusions. An interesting observation in the later (1993) case-control portion of the Belgian study was that hepatitis A virus antibodies were less prevalent in hemophilia patients than in age-matched controls.(ABSTRACT TRUNCATED AT 250 WORDS)