NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) plays pivotal roles in antioxidation and reductive biosynthesis. However, the effect of NADPH treatment on cell survival is unknown. In this study, we determined the effect of NADPH treatment on the survival of glioma cells. Treatment of C6 glioma cells with as low as 1 μM NADPH for 24 hrs induced a significant decrease in the survival of the glioma cells, while NADPH treatment had no effect on the survival of primary astrocyte cultures. We also found that NADPH treatment increased intracellular oxidative stress. Three antioxidants and the NADPH oxidase inhibitor, apocynin, attenuated the effect of NADPH. Poly(ADP-ribose) polymerase (PARP) activation appears to be a downstream effector of the oxidative stress, since PARP inhibitors reduced the effect of NADPH. Calcium chelator, BAPTA-AM, also attenuated the effect of NADPH. Collectively, these data indicate a novel property of NADPH: NADPH decreases glioma cell survival by inducing the NADPH oxidase-dependent increase in oxidative stress and by PARP activation. These results also suggest a potential therapeutic effect of NADPH on gliomas.