AIM:To investigate the prevalence of hepatitis G virus(HGV)infection and to analyse the homology of different HGV strainsin Southern China.METHODS:A total of 1993 sera from different groups inGuangdong,Hong Kong,and Yunnan were detected byreverse transcription polymerase chain reaction(RT-PCR).The nucleotide sequences of 5’untranslated region(5’UTR)derived from 20 strains and NS5 region from 3 strains weredetermined.RESULTS:The positive rate of HGV RNA was 0.89 % incommunity population,2.57 % in blood donors,17.86 % inintravenous drug abusers,14.13 % in patients withhemodialysis,13.66 % in those with hepatocellularcarcinoma,25.30 % in non A-E hepatitis,7.22 % in hepatitisB,12.73 % in hepatitis C,41.67 % in patients receivedbone marrow transplantation,respectively.The homologywas 90.40-100 % in 5’UTR among different strains,whilethat of NS5 region was 93.3-94 % in nucleotide sequence,and 97-99.2 % in amino acid sequence.CONCLUSION:These results showed that there was a highincidence of HGV infection in patients from Southern China,being treated for bone marrow transplantation,hepatocellularcarcinoma and those on haemodialysis.Furthermore,therewas also a high frequency of co-infection of HGV with HBV,HCV,non A-E viral hepatitis and that among intravenousdrug abusers.The study also showed that sequence variationin different strains was associated with geographical factorsbut there was no significant difference in 5’UTR in circulatingviruses between different patient groups.Finally,by sequential analysis of viral species present in individualpatients over a three months period there was no evidenceof sequence variation in the 5’UTR. AIM: To investigate the prevalence of hepatitis G virus (HGV) infection and to analyze the homology of different HGV strains in Southern China. METHODS: A total of 1993 sera from different groups inGuangdong, Hong Kong, and Yunnan were detected byreverse transcription polymerase chain reaction (RT-PCR) .The nucleotide sequences of 5’untranslated region (5’UTR) derived from 20 strains and NS5 region from 3 strains were determined .RESULTS: The positive rate of HGV RNA was 0.89% incommunity population, 2.57% in blood donors , 17.86% inintravenous drug abusers, 14.13% in patients with hepatocellular carcinoma, 13.66% in those with hepatocellularcarcinoma, 25.30% in non AE AE, 7.22% in hepatitis B, 12.73% in hepatitis C, 41.67% in patients receivedbone marrow transplantation, respectively. 90.40-100% in 5’UTRs among different strains, while att of NS5 region was 93.3-94% in nucleotide sequences, and 97-99.2% in amino acid sequences. CONCLUSION: These results showed that there was a highincidence of H GV infection in patients from Southern China, being treated for bone marrow transplantation, hepatocellularcarcinoma and those on haemodialysis. Still more, therewas also a high frequency of co-infection of HGV with HBV, HCV, non AE viral hepatitis and that among intravenous drug abusers. study also showed that sequence variationin different strains was associated with geographical factors but there was no significant difference in 5’UTR in circulatingviruses between different patient groups. Notally, by sequential analysis of viral species present in individualpatients over a three months period there was no evidence of sequence variation in the 5’UTR.