The effects of the endogenous antioxidant glutathione (GSH) on MDMA-induced neurotoxicity was examined in Dark Agouti rats by performing a series of studies wherein glutathione was depleted before and during a neurotoxic regimen of MDMA. Glutathione depletion was accomplished through administering buthionine-(S,R)-sulfoxamine (BSO), a glutathione synthesis inhibitor, the direct glutathione conjugator diethylmaleate (DEM), or a combination of BSO and DEM. Glutathione depleting drugs were either administered along with saline or with 12.5 mg/kg MDMA. They found that only DEM attenuated reduction in hippocampal, striatal and cortex serotonin (measured via HPLC). However, DEM also attenuated elevation in body temperature after MDMA administration, suggesting that its neuroprotective effects were largely due to reducing hyperthermia. When administered alone, BSO exacerbated MDMA-induced reduction in brain 5-HT in hippocampus, striatum and cortex and failed to reduce hyperthermia. Examining concentration of GSH in liver and brain demonstrated that glutathione was successfully depleted by BSO and DEM (more so by DEM). While it was originally suggested that conjugation between glutathione and an MDMA metabolite might be harming 5-HT neurons (Esteban et al. 2001), study findings reported here indicate that glutathione conjugates may not play a role in MDMA neurotoxicity. The neurotoxic or neuroprotection potential offered by glutathione was not tested in this series of studies, as they did not examine the effects of glutathione augmentation. These findings also fail to support the hypothesized role of hepatic glutathione conjugates in MDMA neurotoxicity, since signs of liver glutathione depletion were not related to attenuated reduction in 5-HT after MDMA.