Epidemiological investigations of GB virus C (GBV-C)/hepatitis G virus (HGV), an infectious agent discovered in 1995/1996, are facilitated by a recently developed immunoassay for the detection of antibodies to the viral envelope 2 protein (anti-E2). We used this assay to establish GBV-C/HGV prevalence in seven European, African, and Asian countries. A total of 1579 serum samples from healthy adults lacking prior exposure to known parenteral risk factors was screened. Anti-E2 positivity ranged from 13.6% (Italy) to 7.7% (Mauritius) in the European and African countries investigated. Anti-E2 prevalence was exceedingly low in the Philippines and Sri Lanka. This observation might be attributable to socio-economical and demographic factors.