The authors present a commentary on findings reported by Reneman and colleagues, with the commentary appearing in the same issue of Archives of General Psychiatry as the original paper. The authors express support for continued brain imaging research examining ecstasy users and non-users that targets specific brain regions (e.g. hippocampus). They also address the sensitivity of b-CIT binding as a measure SERT site density. The commentary discusses dissociation between changes in the serotonin system and neurocognitive performance in comparisons of ecstasy users and non-users. McCann and colleagues suggest that findings in non-human primates should be used as a good guide for judgments concerning human neurotoxicity, and also voices support for longitudinal studies of ecstasy users that will be able to detect recovery as well as long-lasting effects.