Ketoconazole is an imidazole antifungal agent which inhibits the biosynthesis of fungal cellmembrane ergosterol and has immunosuppressive properties in vitro. Biphenyl dimethyl dicarboxylate (PMC) has been utilized for antioxidative action and for liver-protective purposes. Studies were undertaken to investigate effects of biphenyl dimethyl dicarboxylate (PMC) on the immunosuppression of ketoconazole in ICR mice. In the combination of PMC and ketoconazole, as compared with the treatment of ketoconazole alone, there were significant increases in activities of natural killer (NK) cells and phagocytes along with circulation leukocytes. The elevation of serum glutamic-pyruvic transaminase (S-GPT) and total protein levels caused by ketoconazole were reduced by the combination of PMC and ketoconazole. In addition, lower serum albumin and albumin/globulin (A/G) ratio were also increased to normal level.