Sophora flavescens AITON (Leguminosae) is a typical traditional Korean medical herb considered to exhibit antibacterial, anti-inflammatory, and antipyretic effects, and is also used for the treatment of skin and mucosal ulcers, sores, diarrhea, gastrointestinal hemorrhage, arrhythmia, and eczema. In this study, the compound sophoraflavanone G was isolated from the dried roots of S. flavescens by bioassay-guided fractionation. We then investigated the effects of various concentrations of sophoraflavanone G on cell viability and the induction of apoptosis in KB cells after an incubation of 24 hr. The results were determined by the following methods: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-terazolium bromide (MTT) assay, Hoechst-33258 dye staining, flow cytometry (cell cycle), and Western blotting for caspase-3 and poly (ADP-ribose) polymerase (PARP). We found sophoraflavanone G induced the apoptosis of KB cells in a dose-dependent manner that was verified by DNA fragmentation, apoptotic bodies, the sub-G1 ratio, caspase-3 activity, and cleavage of PARP. These results suggest that sophoraflavanone G has potent anti-proliferative effects on human oral epidermoid carcinoma cells, with the induction of apoptosis.