The Cytotoxic activity of the ethyl acetate soluble fraction of Perilla frutescens on human oral epithelioid carcinoma cell lines was evaluated by 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyl-2H-tetrazalium bromide (MTT) colorimetric method. The light microscopic study was carried out to observe the morphological changes of cultured human oral epitheloid carcinoma cell lines (KB) These results were obtained as follows; 1. subfraction 1 of the ethyl acetate soluble fraction of perilla frutescens was shown significant cytotoxic activity (p<0.001) at 10-2 mg/ml concentration, this concentration was decreased the cytotoxic activity of 70.3% . 2. The comparison of IC50 values of various subfractions in human oral epithelioid carcinoma cell lines was exhibited that their susceptibility to these subfractions decreased in the following order ; subfraction 5 > subfraction 4 > subfraction 3 > subfraction 2 > subfraction 1 by MTT assay. In light microscopy, the subfraction 1 of the ethyl acetate soluble fraction of Perilla frutescens showed the highest cytotoxic activity. These findings suggest that subfraction 1 possessed the most cytotoxic constituents.