The cytotoxic effect of benzoic acid and related compounds on the growth of normal cell lines and human oral epithelioid cell line was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and 2,3-bis-[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-caboxanilide (XTT) methods. 3,4,5-Trihydroxybenzoic acid decreased the cell viability of human oral epithelioid cells and the cell adhesion activity of human oral epithelioid cells. Under the light microscopy, 100 ${mu}M$ 3,4,5-trihydroxybenzoic acid showed the highest cytotoxic activity. From these results, we can propose that 3,4,5-trihydroxybenzoic acid has a potential anticancer activity.