The purposes of this study were to measure the cytotoxic effect of alpha-mangostin on head and neck squamous cell carcinoma (HNSCC) cell lines, to evaluate the apoptotic aspect of dead cells, and to identify the molecular mechanism involved in apoptosis.The human HNSCC cell lines HN-22, HN-30 and HN-31 were treated with alpha-mangostin. The apoptotic effects of alpha-mangostin on HNSCC cells were determined by observation the morphological changes of cells, immunofluorescence for single-stranded DNA (ssDNA), and DNA fragmentation analysis. The expression of bax, bcl-2, and p53 were detected by RT-PCR and Western blot analysis.Alpha-mangostin showed excellent apoptotic effects on HNSCC cell lines, which induced the down-regulation of bcl-2, but up-regulation of bax and p53 in HN-22, HN-30 and HN-31.The present study suggests that the induction of apoptosis by alpha-mangostin seemed to be modulated by bcl-2, bax and p53 level in HNSCC cell lines.