OBJECTIVE: To investigate the serum levels of soluble Fas antigen (sFas), soluble intercellular adhesion molecules-1 (sICAM-1), interleukin-18 (IL-18) in patients with chronic hepatitis C and to study their roles in pathogenesis of chronic hepatitis C. METHODS: Serum sFas, sICAM-1, IL-18 levels were measured in 30 cases of chronic hepatitis C before and after treatment of interferon-alpha by enzyme-linked immunosorbent assay (ELISA), serum titer of HCV-RNA was detected by quantitative PCR and serum ALT activity was also detected. RESULTS: Serum levels of sFas sICAM-1 IL-18 in chronic hepatitis C patients were significantly higher than those in normal controls (P<0.01), showing correlation with serum HCV-RNA titer (r=0.915, r=0.795, r=0.757, respectively, P<0.01), Serum levels of sICAM-1, IL-18 showed correlation with serum ALT level(gamma=0.952, gamma=0.969, respectively, P<0.01), but no relationship was observed between serum sFas and serum ALT level(P>0.05). Serum levels of sFsa sICAM-1 IL-18 markedly decreased in responsive patients while no change was observed in patients with no response after treatment. CONCLUSION: Soluble Fas, soluble ICAM-1, IL-18 may participate in the pathogenesis of chronic hepatitis C and show correlation with the severity of histological inflammation and viral titer.