The incidence and clinical significance of GB virus C/hepatitis G virus(GBV-C/HGV) infection were evaluated in 68 patients on maintenance hemodialysis. GBV-C/HGV RNA was identified in serum by a reverse transcription-polymerase chain reaction assay with nested primers deduced from a nonstructural region. Hepatitis B surface antigen(by RIA) and anti-hepatitis C(by ELISA) were checked simultaneously. Out of 68 patients, GBV-C/HGV RNA was detected in 5(7.4%), HBsAg in 4 patients(5.9%) and anti-HCV in 15 patients(22%). All 5 patients with positive GBV-C/HGV RNA had a history of blood transfusion. Out of 5 patients with positive GBV-C/HGV RNA, 2 patients were coinfected with hepatitis C virus, who showed chronic hepatitis clinically. Three patients with isolated GBV-C/HGV infection showed normal liver function during last 18 months' period. Between the patients with positive GBV-C/HGV RNA and those with negative GBV- C/HGV RNA, there was no difference in age, sex, duration of hemodialysis and amount of transfusion. Our data suggest that GBV-C/HGV infection may be present, with or without hepatitis C virus infection, in maintenance hemodialysis patients. Although the liver function of patients with isolated GBV-C/ HGV infection was normal, the clinical significance of this new virus remains to be determined.