The role of interleukin-17 (IL-17) in autoimmune hepatitis (AIH) was investigated. A mouse model of experimental autoimmune hepatitis was established, and the syngeneic S-100 antigen emulsified in complete Freud's adjuvant was injected intraperitoneally into adult male C57BL/6 mice. The IL-17 expression in serum and the livers of the mice models was detected by using ELISA and immunohistochemistry, respectively. IL-17 neutralizing antibody was used to study the biological effect of IL-17 in the experimental AIH. IL-17 neutralizing antibody in vivo administration alleviated the hepatic inflammation and ALT level in the AIH model. IL-17 in the peripheral blood mononuclear cells (PBMC) of AIH patients was measured by using real-time PCR method. The results showed that IL-17 level was significantly up-regulated in AIH patients and mice models. It was concluded that IL-17 contributed to the development of AIH and might be a potential therapeutic target of AIH.