Objective　Investigation of the role of mitochondrial membrane potential (MMP) in the homoharringtonine (HHT)-induced apoptosis. Methods　Annexin V staining, flow cytometry and confocal laser scan microscopy were used to observe the relationship between Bax, cytochrome C and MMP in the HHT-induced apoptosis of leukemic T lymphocytic line Molt-3. Results　The induction of apoptosis by HHT resulted in the translocation of Bax from cytosol to mitochondrial membrane and the decrease of cellular MMP, followed by the release of cytochrome C from mitochondria to cytosol. Conclusions　Changes of mitochondrial membrane potential might play a critical role in the HHT-induced apoptosis of leukemic T-cells.