BACKGROUND: Monascus-fermented products are among the most commonly used traditional food supplements. Dioscorea is known to exhibit anticancer properties. In this study the effects of the ethanol extract of red mold dioscorea (RMDE) on cell proliferation, cell cycle and apoptosis in human oral cancer cells were investigated. RESULTS: RMDE exercised growth inhibition on squamous cell carcinoma-25 (SCC-25) cells. RMDE-mediated G2/M phase arrest was associated with the down-regulation of NF-κB, resulting in the inhibition of cyclin B1 and CDK1 expression; this may be the mechanism by which RMDE inhibits cancer cells. Furthermore, the proapoptotic activity of RMDE was revealed by the Annexin V-FITC/PI double-staining assay. In addition, the proapoptotic effect of RMDE was evident by the inhibition of Bax expression in the mitochondria, resulting in the activation of caspase-9 and caspase-3 and subsequent triggering of the mitochondrial apoptotic pathway. RMDE also enhanced caspase-8 activity, indicating the involvement of the death receptor pathway in RMDE-mediated SCC-25 cell apoptosis. CONCLUSION: RMDE treatment inhibited the growth of SCC-25 cells by arresting cell cycle at the G2/M phase and induced apoptosis in a time- and dose-dependent manner. Therefore RMDE may be a good candidate for development as a dietary supplement against oral cancer.