The differentiation of leukemia cells into mature cells is a major target of the human leukemia therapy. As differentiated leukemia cells lose their proliferative and tumor-forming abilities, differentiation inducers may be useful for the treatment of leukemia. In this study, the experiments were designed to determine whether diallyl disulfide (DADS) regulates expressions of tumor suppressor protein PTEN (phosphatase and tension homologue) in HL60 cells. DADS causes upregulation of PTEN in a time- and dose-dependent manner, which was correlated with decrease of phospho-Akt level. These results suggest that DADS induces upregulation of PTEN in human leukemia cells. These results suggest that DADS may be a useful anticancer agent for management of human leukemia.