Since the identification of the new human virus, GB virus C (GBV-C)/hepatitis G-virus (HGV), in 1995/1996, reverse transcription polymerase chain reaction remained the sole available diagnostic tool for GBV-C/HGV infection. Recently, a serologic test based on the detection of antibodies to the putative envelope protein 2 (anti-E2) has been introduced. We used this assay for a seroepidemiological survey including 3,314 healthy individuals from different parts of the world, 123 patients from Germany who were suspected to have an increased risk of acquiring GBV-C/HGV infection, 128 multiple organ donors, and 90 GBV-C/HGV RNA positive persons. In European countries, anti-E2 seropositivity ranged from 10.9% (Germany) to 15.3% (Austria). In South Africa (20.3%) and Brazil (19.5%), even higher anti-E2 prevalence rates were recorded. In Asian countries like Bhutan (3.9%), Malaysia (6.3%), and the Philippines (2.7%), anti-E2 positivity was significantly lower. GBV-C/HGV anti-E2 prevalence in potential "risk groups," i.e., patients on hemodialysis and renal transplant recipients, did not vary significantly from anti-E2 seroprevalence in German blood donors. Anti-E2 and GBV-C/HGV RNA were found to be mutually exclusive, confirming the notion that anti-E2 has to be considered as a marker of past infection.