Aim: To gain more insight into the reasons and motives why people do not start taking ecstasy. Method: As part of the NeXT Study, we prospectively monitored 188 subjects who were ecstasy-naive at baseline but seemed likely to take ecstasy (MDMA) of their own accord during the course of the study. After an 11- to 26-month follow-up period, 160 respondents remained (85.1%). Among these, 65 participants started taking ecstasy (novel ecstasy users, NEUs) and 95 did not (persistent non-users, PNUs). Several times during their participation, subjects completed lists of reasons and motives for not taking ecstasy. Findings: Principal components analysis identified three main factors associated with non-use: rationality (factor score 0.491), lack of opportunity (0.229) and fear of the effects of ecstasy (0.211). At baseline, PNUs scored higher than NEUs on all three factors. For the NEUs, no significant changes occurred over the course of the study in all three factor curves. Slight shifts were seen for PNUs--the fear of effects diminished and lack of opportunity grew; scores on rationality remained constant. Conclusions: NEUs and PNUs were distinguished most clearly by their factor scores on rationality. Some valuable insights for prevention are discussed. (Contains 3 tables and 1 figure.)