This is a review of the physiological and psychological effects of MDMA in humans and non-human animals written for an audience of psychiatrists and psychologists, focusing on effects in humans. The review covers patterns of ecstasy use, MDMA pharmacology, physiological and psychological (subjective) effects, adverse effects and fatalities after ecstasy use, and long-term effects of ecstasy use. The paper begins with a brief history of MDMA and concludes with a critical examination of studies of long-term effects of repeated ecstasy use, and a plea for conducting more research using better research designs. The strengths of this review are its comprehensive scope, its section on physiological effects and in the critique of studies of ecstasy users. For instance, the section on physiological effects relies on information from human clinical trials, reports from ecstasy users, and studies in non-human animals. Some elements of the critique have been previously presented (Cole et al. 2002), but with the addition of comments on the effects of polydrug use on assessments of ecstasy users. The authors' conclusions that psychological problems are more likely an antecedent to drug use, and not the result of ecstasy use, are confirmed by recent publications not cited in this review (e.g. Daumann et al. 2001; Lieb et al. 2002; Morgan et al. 2002; Thomasius et al. 2003). The weakest point of this review is the section on MDMA pharmacology, due in part to the attempt to cover acute pharmacological effects and effects relating to neurotoxicity in the same section. While the information provided is correct, it is not always clearly organized, and the reader must separate acute effects from effects related to neurotoxicity. In the pre-clinical pharmacology section, the authors state that MDMA releases dopamine through 5HT2A receptors, yet there are several reports of direct effects on dopamine release (see for instance Battaglia et al. 1988; Crespi et al. 1997; Fitzgerald and Reid 1993). In the physiological effects section, the authors suggest that coadministration of MDMA and serotonin uptake inhibitors (like Prozac) might lead to serotonin syndrome, yet previous findings from case reports and a laboratory study report that acute MDMA effects are reduced, not increased, after SSRI coadministration (Liechti et al. 2000; McCann et al. 1993; Stein and Rink 1999). Also in this section, the authors state that MDMA is most likely metabolized via CYP2D6. However, recently reported findings from human trials and in vitro studies (Pizarro et al. 2003; 2002; Kraemer and Maurer 2002) suggest that MDMA is broken down by other enzymes besides CYP2D6 In examining their critique, it should also be noted that recent publications have more consistently employed polydrug-using control groups (for example, see Gouzoulis-Mayfrank et al. 2000; Fox et al. 2001), thus somewhat mitigating the confounding effects of polydrug use in these studies. This review is notable in its attempts to compare the effects of MDMA with the effects of other drugs. This comparison allows readers to consider findings in the context of how drugs effect brain neurotransmitter levels and cognition rather than treating MDMA as uniquely possessing such effects.