Purpose: The main aim of this study was to determine the effects of querctrin (3,5,7,3`,4`-tetrahydroxyflavone) and rutin (quercetin-3-O-rutinoside) on the induction of cell growth and apoptosis in human oral cancer cell, Materials and Methods: The effects of quercetin and rutin on cell growth and apoptosis induction in human oral cancer cells were examined using a MTT assay, nuclear staining with DAPI, immunoblotting and a determination of caspase activation in KB human oral cancer cells. Results: Quercetin inhibited the growth of KB cells in a concentration- and time-dependent manner but rutin did not have a significant effect on the cell viability of KB cells. Treatment of KB cells with quercetin resulted in nuclear condensation and fragmentation, whereas rutin had little effect on nuclear condensation and fragmentation. Quercetin time-dependently promoted the proteolytic cleavage of procaspase-3 in KB cells with increasing amounts of cleaved caspase-3. On the other hand, rutin did not promote significant proteolytic cleavage of procaspase-3. The proteolytic processing of caspase-7 in KB cells was increased by quercetin but not by rutin. Quercetin promoted the proteolytic cleavage of procaspase-9 with increases in the amount of cleaved caspase-9, whereas rutin did not. The activation of caspase-3 and -7 in living KB cells treated with quercetin was detected by fluorescence microscopy but rutin did not lead to significant caspase-3/-7 activation in the cells. Conclusion: Querctin strongly inhibits cell proliferation and induces apoptosis in KB human oral cancer cells, and might have potential properties for anti oral cancer drug discovery.