In this study, the authors evaluated the possible use of 3-hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in anti-leukemic chemotherapy. Cytotoxic potency against HL-60 was as follows; simvastatin (SV)>atorvastatin>cerivastatin>fluvastatin. Interestingly, HL-60-R2, an all-trans retinoic acid (ATRA)-resistant HL-60 variant, was twice as sensitive to SV than HL-60. Further studies revealed the particular mechanism of action of SV-induced apoptosis in leukemia. SV directly and rapidly disordered mitochondria with a loss of its membrane potential, reactive oxygen species (ROS) generation and subsequent irreversible damage with cytochrome c leakage and, finally, SV induced apoptosis through caspase-9 activation, whereas several studies have shown that other statins induced apoptosis to leukemia by the depletion of isoprenoids used for the prenylation of small GTPases, which are essential for cellular signal transduction. Our findings suggest that the mitochondrial pathway plays an important role in the higher potency of SV as a new class of agents for anti-leukemic therapy alone and/or in combination with agents.