Objectives : In order to evaluate the cytotoxicity of 3,4,5-trihydroxybenzoic acid and related compounds on the growth of normal cell lines and human oral epithelioid cell line, cell viability, cell adhesion ability, and morphological changes of cells were examined. Methods : We measured the cytotoxicity of 3,4,5-trihydroxybenzoic acid and related compounds with 3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyltetrazolium bromide-[MTT), and 2,3-bis-[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium -5-caboxanilide-[XTT) methods. Results : The cytotoxicity of 3,4,5-trihydroxybenzoic acid($IC_{50}$, $2,552.40;{mu}M$) was low according to the toxic criteria. Cytotoxic effect of 3,4,5-trihydroxybenzoic acid and related compounds against $IC_{50}$ value in cell morphology increased in a concentration-dependent manner. In light microscopy, $100;{mu}M$ 3,4,5-trihydroxy-benzoic acid showed th highest cytotoxic activity. Conclusions : These results suggest that 3,4,5-trihydroxybenzoic acid may have a potential anticancer activity.