2-Methoxyestradiol (2-ME), an endogenous metabolite of 17beta-estradiol, induces the intracellular accumulation of superoxide anion (O2*-) and buthionine sulfoximine (BSO) is an inhibitor of glutathione (GSH) synthesis. We have examined the combination anticancer effect of 2-ME and BSO accompanied with hydrogen peroxide (H2O2). 2-ME inhibited cell growth in renal carcinoma cell lines (ACHN and ACVB) accompanied by an increase in the intracellular contents of GSH. The combination of 2-ME, BSO and H2O2 showed a significant antiproliferation effect in both ACHN and ACVB. The intracellular levels of reactive oxygen species (ROS) with a combination with 2-ME and H2O2 in ACHN and ACVB pretreated with BSO were markedly increased, which may have contributed to the potential antiproliferative action.