Differences in the drug use characteristics and psychosocial variables in the use and non-use of ecstasy within 845 16–25 year-olds in the UK was examined. Based on levels of ecstasy use and intentions, two groups of non-users (resistant and vulnerable), three groups of users (light, moderate and heavy) and an ex-user group were identified. It was found that there is predictive utility in this way of expanding the widely employed ‘user versus non-user’ dichotomy. Resistant non-users were more likely to be younger, female, and were characterized by lower levels of use of four other drugs (amphetamine, cannabis, cocaine and LSD). Those ‘at risk’ of using ecstasy reported more frequent use of amphetamine, LSD, and cannabis than resistant non-users. Heavy user groups reported using amphetamine, cocaine and LSD more frequently than all the other groups. Having ecstasy using friends increased the odds of being an ‘at risk’ non-user or an ecstasy user. Normative influence also differentiated between the three user groups (light, moderate, and heavy). Beliefs about ecstasy use being immoral, ecstasy offers being difficult to resist, ecstasy use making one feel guilty and ecstasy being readily available differentiated between user and non-user groups. These factors could usefully inform the content of health education materials designed to change ecstasy use. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]