This study was carried out to determine the prevalence of antibodies to herpes simplex virus types 1 (HSV-1) and 2 (HSV-2) in selected German populations, such as blood donors, hospital patients, and human immunodeficiency virus (HIV)-seropositive individuals. Serum samples collected between 1996 and 1998 were tested by enzyme immunoassays using monoclonal antibody-selected native gG1 and gG2 as antigens and an immunoblot using type-specific recombinant glycoproteins. Equivocal results were resolved by an "in-house" Western blot assay. The prevalence of HSV-1 antibodies increased steadily with age and reached high levels of Ն88% among subjects 40 years of age or older. In the sample of patients and blood donors, the HSV-2 seroprevalence was 12.8% (95% CI = 11.9-13.8%). About 81% of the HSV-2 seropositive subjects were coinfected with HSV-1. When adjusted for age, there was no difference in the HSV-2 seroprevalence between hospital patients and blood donors. The HSV-2 seroprevalence was significantly higher among women (15%) than among men (10.5%), yielding a female : male odds ratio of 1.5 for hospital patients and of 1.67 for blood donors. Among the HIVinfected population, 91.1% were seropositive for HSV-1 and 47.9% for HSV-2. HIV-infected women have a significantly higher risk of HSV-2 infection than men (odds ratio [OR] = 3.22; 95% confidence ratio [CI] 1.99-5.20). In conclusion, although the rate of infections with HSV-2 is relatively low in the German population, attention should be given to the further development in adolescents, especially in view of a possible decrease of HSV-1 seroprevalence in childhood.