To investigate the features of various hepatitis virus infection in intravenous drug users (IVDU), we conducted an epidemiological survey of hepatitis viruses including hepatitis B virus (HBV), hepatitis C virus (HCV), hepatitis D virus (HDV) and hepatitis G virus (HGV) in IVDU. The correlation of TH lymphocyte cytokine and hepatitis virus infection was examined. A study population of 406 IVDU consisted of 383 males and 23 females. HBV-DNA and HCV-RNA were detected by fluorescence quantitative polymerase chain reaction. HBsAg, HBeAg, anti-HBc,anti-HCV, HDV-Ag and anti-HGV were assayed by ELISA. The levels of cytokines of TH 1 and TH2 were measured by ELISA. The similar indices taken from 102 healthy persons served as controls. The infection-rate of each virus among IVDU was 36.45 % for HBV, 69. 7 % for HCV,2.22 % for HDV, and 1. 97 % for HGV, respectively. The co-infection rate of HBV and HCV was detected in 113 of 406 (27. 83%). In contrast, among controls, the infection rate was 17.65 % for HBV and 0% for the other hepatitis viruses. The levels of PHA-induced cytokines (IFN-γ and IL-4) and the level of serum IL 2 were obviously decreased in IVDU. On the other hand, the level of serum IL-4 was increased. The IFN-γ level was continuously decreased when the IVDU was infected with HBV/HCV. In conclusion, HBV and HCV infection were common in this population ofIVDU and they had led to a high incidence of impaired TH 1 cytokine levels.