Despite increasing use of the illicit substance known as ecstasy, there is a paucity of research concerning psychosocial correlates of its use. A prospective study examined the ability of variables specified by the theory of planned behavior (TPB) to predict ecstasyuse intentions and behavior. Regression analyses showed that theory of reasoned action and TPB variables provided good prediction of intentions to use the substance. Moreover, support was obtained for a distinction between perceptions of behavioral control over taking ecstasy vs. control over obtaining the substance in the prediction of intentions. Habit contributed additional variance to the prediction of intentions, and reduced the effects of perceived behavioral control over taking ecstasy to nonsignificance. Ecstasy use over 2 months was directly predicted from intentions to use the substance.