Cyclosporine A is an immunosuppressant commonly used for patients receiving organ transplants. Gingival overgrowth is an adverse side-effect seen in about 8-26% of patients taking cyclosporine A which have been shown to increase the DNA synthesis of gingival -9 fibroblast at the concentration of 10 gpnl in vitro. Glycyrrhetinic acid is the active pharmacological ingredients of licorice which exerts steroid-like action and anti-viral activity. Oleanolic acid, which were isolated from Glechoma hederacea, has been shown to act as inhibitors of tumor promotion in viuo and to be less cytotoxic retinoic acid. This study has been performed to evaluate the effects of glycyrrhetinic acid and oleanolic acid on cyclosporine A induced cell activity in vitro. Human gingival fibroblasts were isolated from explant cultures of healthy gingiva of orthodontic patients. Gingival fibroblasts were trypsinized and transferred to the walls of -9 microLest plates. Fibroblasts were cultured in growth medium added 10' g+l cyclosporineA and 50pl+l lipopolysaccharides. Cells between the 4th and 6th transfer in culture were used for this study. The morphology of gingival fibroblst were examined by inverted microscope. The effects of cyclosporine A on the time course of DNA sythesis by human gingival fibroblasts were assessed by [H]-thymidine uptake assays. Cyclosporine A was found to stimulate DNA synthesis of human gingival fibroblast at a concentration -9 of 10 g+l. In the presence of lipopolysaccharide derived from Fusobacterium nucleatum, addition of cyclosporine A results in reversal of inhibition at the coneentration which normally inhibits gingival fibroblast proliferation. The cell acitivities in the presence of glycyrrhetinic acid and oleanolic acid were decreosed, and increased cell acitivities by cyclosporine A were decreased by glycyrrhetinic acid and oleanolic acid at the concentration of 200pgl. These results suggested that the increased cell activities by cyclosporine A modulated by glycyrrhetinic acid and oleanolic acid.