The participation of cytokines in the early stage mechanism of hepatocyte proliferation has already attracted attention. We investigated the effect of methylprednisolone (MDS), which inhibits the inflammatory response, given before and after a 70% partial hepatectomy in rats on the kinetics of tumor necrosis factor-alpha and Interleukin-6, liver cell function and the rate of liver regeneration. Serum Interleukin-6 levels of the MDS groups were significantly lower than those of the control group. Serum alanine aminotransferase, aspartate aminotransferase and hyaluronic acid levels were also significantly decreased, however, the serum albumin level showed high values in the MDS groups. In the MDS groups, MIB-5 labeling indices, a novel antibody reactive with the equivalent Ki-67 protein, which detects immunohistochemically all active parts of the cell cycle in the rat liver, were more pronounced than in the control group at an earlier time. However, in regard to 5-bromo-2-deoxyuridine (BrdU), there were no significant differences among the three groups. There were no differences in residual liver weight/body weight between the three groups after 336 h. In our study, MDS administration before or after a 70% partial hepatectomy decreased serum Interleukin-6 levels, and inhibited hepatic dysfunction. Therefore, we considered that beneficial effects of physiological doses of MDS in the peri-operative period should be confirmed in humans.