The appropriate method of etiologic therapy for gingival overgrowth is yet unknown. In this study drug-induced proliferation of Gin-1 cells, a normal human gingival fibroblast cell line, was examined by using the reagent water-soluble tetrazolium-1. Tranilast (100 μM) inhibited the nifedipine (10 μM)-induced proliferation of gingival fibroblasts. The level of basic fibroblast growth factor (bFGF) was determined by using an enzyme-linked immunosorbent assay kit. Tranilast inhibited the release of bFGF from the cells. In conclusion, tranilast depresses the nifedipine-induced proliferation of gingival fibroblasts by inhibiting the release of bFGF. Administration of tranilast may thus be clinically effective for the treatment of gingival overgrowth.