In the present study, we have evaluated cytotoxic effects of Taraxaci Herba extract in human oral epitheloid carcinoma cells. An antitumor activity was measured by colorimetric assays using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and sulforhodamine protein B (SRB). The light microscopic study showed morphological changes, Ag-NOR (argyrophylic nucleolar organizer region) number and PAS positive reaction or the treated cells. These results obtained are as follows : MTT and SRB quantities were significantly decreased in cultured KB cells treated with 10$^{-2}$ /mg/ml and 10$^{-3}$ /mg/ml concentrations. The number of Ag-NORs were significantly decreased in cultured KB cells treated with 10$^{-2}$ /mg/ml and 10$^{-3}$ /mg/ml concentrations and the rate of Ag-NORs was shifted to left side (one Ag-Nounucleus was increased and five Ag-NORs/nucleus were decreased) by the high concentration. PAS reaction of cultured KB cells treated with 10$^{-2}$ /mg/ml and 10$^{-3}$ /mg/ml concentrations was negative. These results suggest that Taraxaci Herba retains a potential antitumor activity.