This paper studied the effects of physiologically available oxidants on HL 60 differentiation induced by all-trans retinoic acid (ATRA) or dimethyl sulfoxide (DMSO). Hydrogen peroxide (15 μM) and taurine chloramine (200 μM) induced HL 60 differentiation, which was detected by CD11b expression and superoxide production. Cd11b and p67phox mRNA expression was also augmented by these oxidants. In contrast, reducing chemicals, such as dithiothreitol, 2,3-dimercapto-1-propanol and N-acetylcysteine inhibited CD11b expression. Notably, DMSO inhibited methionine sulfoxide reductase activity, induced heme oxygenase-1 (ho-1) mRNA and enhanced oxidant-induced cell death, which indicated that DMSO intensified oxidative stress. After the addition of oxidants, ho-1 expression preceded the cd11b expression. Vicinal dithiol-reactive phenylarsine oxide (50 nM) also increased CD11b expression induced by DMSO or ATRA. These observations suggested that oxidative stress enhanced granulocytic differentiation of HL 60 cells and that leukaemic cell differentiation was affected by cellular redox status.