Hepatitis G virus (GBV-C/HGV), a recently identified RNA virus adds to the risk of parenteral transmitted viral infections in hemodialysis patients. We studied the prevalence of GBV-C/HGV-RNA in serum and peripheral blood mononuclear cells (PMNC) by reverse transcription-polymerase chain reaction (RT-PCR) and determined antibodies against the envelope protein E2 of GBV-C/HGV by ELISA. A total of 119 dialysis patients were studied. GBV-C/HGV-RNA was found in 16 of 119 patients (13%) as compared with 2% of healthy controls (P = 0.014). Two of the 16 GBV-C/HGV-RNA+ patients were co-infected with HCV, and none was positive for HBV-DNA. In 38% of serum GBV-C/HGV-RNA+ patients GBV-C/HGV-RNA was also detected in PMNC. Ln addition, GBV-C/HGV-RNA was identified in PMNC of 2 patients negative for GBV-C/HGV-RNA in serum. Twenty-four patients had anti-E2 antibodies in serum (20%), but were GBV-C/HGV-RNA-. In addition, two of the 16 GBV-C/HGV-RNA+ patients were concomitantly positive for anti-E2 antibodies. Only one of the 16 GBV-C/HGV infected patients had elevated aminotransferases; this patient was co-infected with hepatitis C virus. GBV-C/HGV-RNA positivity was independent on duration of hemodialysis, but GBV-C/HGV-RNA+ patients had received more units of blood in the past. Combined data of past contact, as assessed by anti-E2 antibodies, and present infection, documented by GBV-C/HGV-RNA, indicate a high overall exposure to GBV-C/HGV in dialysis patients.