A reverse transcription polymerase chain reaction assay with nested primers (RT-nested PCR) deduced from the 5' untranslated region of HGV genome was established to detect HGV RNA. By using this assay, we tested the serum samples of 106 paid blood donors, 80 intravenous drug users and 168 cases with viral hepatitis in Shenzhen, China. The positive rates of HGV RNA were 8.5%, 46.3% and 7.7%, respectively. The positive rates of HGV RNA in 61 cases with chronic hepatitis B and 33 cases with chronic hepatitis C were 8.2% and 21.2%. Among the 33 cases with chronic hepatitis C, the positive rate of HGV RNA in 15 cases infected with HCV by blood or blood products was 40.0%, compared with 1.7% in 18 cases without exposure to blood or blood products (P<0.05). The results of this study suggest that HGV infection is common in paid blood donors; the intravenous drug user is the population at high risk for HGV infection; the patients with post-transfusion chronic hepatitis C are often supperinfected with HGV.