Screening for HBsAg, anti-HBc, anti-HCV and ALAT levels is now performed on donated blood to prevent post-transfusion hepatitis. A prospective study of 2,368 blood donors was performed in Guadeloupe (French West Indies) to determine risk factors associated with serologic abnormalities: 571 donations (24%) were positive for at least 1 of the 4 analyzed markers with 3.2% positive for HBsAg, 22% for anti-HBc, 0.8% for anti-HCV and 1.4% with ALAT > or = 45 IU/L. The anti-HCV prevalence was significantly different according to ALAT levels (P < 10(-4)). Transfusion history and work status (worker or serviceman) were found to be risk factors, with an odds ratio of 1.94 for serviceman population. Other unexpected risk factors were: number of years residency in Guadeloupe (progressively increased risk with the number of years), birthplace and residence in southern part of the island as well as the existence of gastrointestinal discomfort unrelated to viral hepatitis (odds ratio = 2.91). The results of this study show a unique epidemiologic situation for hepatitis B virus in Guadeloupe necessitating careful selection of blood donors.