Aims: To determine cytokines associated with the progression of acute hepatic injury (AHI), we comprehensively evaluated the serum levels of 17 cytokines. Methods: We simultaneously measured serum levels of 17 cytokines on admission using a newly developed suspension array protein assay system in 51 patients with AHI, including 15 conventional AHI (CAHI), 15 severe AHI (SAHI) and 21 fulminant hepatic failure (FHF). Results: Interleukin (IL)-6, IL-8 and IL-17 levels were significantly different among the three disease types as determined by one-way analysis of variance, and only the IL-17 level showed a significant elevation in SAHI and FHF than in CAHI. Namely, the IL-17 levels in SAHI and FHF patients were 4.4 (2.0-11.0) (mean [1 .s.d. range]) and 5.6 (2.0-18.5) pg/mL, respectively, whereas all CAHI patients showed levels lower than the lower limit of detection (2.0 pg/mL). In multiple regression analysis for each factor of model for end-stage liver disease (MELD) score, only IL-10 level was selected as the significant independent variable for total bilirubin level, only IL-17 level for prothrombin time, and TNF-alpha and IL-1 beta levels for creatinine level. Conclusions: These data suggest the usefulness of serum IL-17 level in evaluating the severity of AHI, thus emphasizing the necessity for the basic investigation of the pathological role of IL-17 in acute hepatitis.