At present, the controversy concerning possible cumulative brain damage due to recreational MDMA/ecstasy use is limited to the drug’s purported actions on the serotonin system, as revealed by high-dose studies in animals. For this reason, claims of MDMA-induced neurotoxicity and associated cognitive deficits or other problems in ecstasy users must be scrutinized carefully. At present, the accumulated evidence for such claims is not compelling for a number of reasons, including (1) inconsistent findings on the existence and reversibility of persistent ecstasy-related serotonergic and cognitive deficits; (2) lack of clear association between changes in brain imaging measures and functional deficits attributed to MDMA-induced neurotoxicity; (3) the contribution of concomitant cannabis or other drug use to both brain imaging abnormalities and cognitive deficits; (4) methodological shortcomings; (5) the questionable relevance of animal models of MDMA-induced neurotoxicity to typical human patterns of ecstasy use; and (6) the potential role of inherent pre-drug deficits in serotonergic systems, impulse control, and executive cognitive function. Ecstasy is the popular term for the serotonin-releasing agent 3,4-methylenedioxy-mehtamphetamine (MDMA). MDMA is a widely abused illicit drug with mixed stimulant and mild hallucinogenic actions. The widespread use of ecstasy/MDMA by young Australian adults raises concern over the health consequences of such behavior. Recent research suggests that MDMA can cause lasting disruptions to the serotonergic system and ecstasy use is commonly associated with deficient cognitive and memory performance. The possibility of cumulative brain damage as a result of its repeated use or heavy use over time presents an alarming prospect. This critical review of the recent research literature on this topic suggests that while studies have improved considerably since the 1990s, the evidence to date remains vague. References