The popular recreational drug Ecstasy (3,4-methylenedioxymethamphetamine, or MDMA, and related congeners) is neurotoxic upon central serotonergic systems in animal studies. So far, the most convincing evidence for neurotoxicity-related functional deficits in humans derives from neurocognitive studies demonstrating dose-related memory problems in Ecstasy users. The aim of the current investigation was to study the relationship between the psychological profile of recreational Ecstasy users and the patterns of their drug use. Twenty-eight abstinent recreational Ecstasy users with concomitant use of cannabis only and two equally sized, matched groups of cannabis users and non-users were administered standardized self-rating scales for the assessment of psychological problems which are thought to be related to central serotonergic function. Ecstasy users had elevated scores on subscales measuring impulsiveness, anxiety, sensation seeking, somatic complaints, obsessive-compulsive behavior and psychoticism. Higher scores were associated with both heavier Ecstasy and heavier cannabis use. After controlling for cannabis use, most group differences in psychometric scores no longer achieved statistical significance. The present data are in line with other reports demonstrating a broad range of psychological problems in Ecstasy users. However, the concomitant use of other drugs, specifically cannabis, seems to be crucial in this respect. Therefore, compared with cognitive deficits, psychological problems appear to be less suitable functional indices of Ecstasy-related neurotoxic damage of central serotonergic systems in humans. Copyright © 2001 John Wiley & Sons, Ltd.