EGb 761, extracted from Ginkgo biloba leaves, has been proven to induce caspase-3-dependent apoptosis in oral cavity cancer cells. Since EGb 761 is a composition of various components, it is important to identify which components are responsible for its anticancer effects to reduce the total dosage and to avoid toxicity. Therefore, the study aimed to determine the effective compounds of EGb 761 that induce apoptosis in oral cavity cancer cells and to identify whether caspase-3 was involved in apoptosis of oral cancer cells by EGb 761 components. The results of cell proliferation assays on oral cavity cancer cells showed that kaempferol and quercetin significantly inhibited cellular proliferation at a concentration of 40 microM. Flow cytometry showed that the antiproliferative effects of each component were due to increased apoptosis. Kaempferol and quercetin induced apoptosis in various oral cancer cell lines (SCC-1483, SCC-25 and SCC-QLL1) and showed cleavage of poly (ADP-ribose) polymerase (PARP). Caspase-3 activity assay revealed that induction of apoptosis by kaempferol and quercetin was caspase-3-dependent. In conclusion, the results suggest that kaempferol and quercetin, two components of EGb 761, effectively induce caspase-3-dependent apoptosis of oral cavity cancer cells and can be considered as possible anti-oral cavity cancer agents.