Arsenic trioxide (As2O3, ATO) is a recently developed drug for the effective treatment of acute promyelocytic leukemia (APL). Experimental studies showed that in vitro differentiation-inducing ability on APL cells of this drug is not significant compared with its in vivo activity. We unexpectedly found recently that hypoxia-mimetic agents and moderate real hypoxia triggered acute myeloid leukemic cells to undergo differentiation. Furthermore, intermittent hypoxia significantly prolonged the survival of the transplanted leukemic mice with inhibition of infiltration and induction of differentiation of leukemic cells. In the following works, molecular mechanisms of hypoxia-induced differentiation were investigated and some interesting results have been obtained. This review will shortly summarize the related progresses and discuss the questions remained to be further investigated.