The study found that those with a higher prevalence of lifetime ecstasy use exhibited higher levels of aggressive and violent behavior. The more ecstasy a person had used in his/her lifetime, the greater variety of violent acts he/she committed. The chances of committing more types of violent acts in the past year increased almost linearly with the number of ecstasy pills ever used. The reverse was true for the odds of committing no violent acts in the past year. Ecstasy use had little effect on the level of aggression among individuals with low self-control; however, the effect of ecstasy on aggression was pronounced for those with high self-control, to the extent that those with high self-control were more aggressive than those with low self-control. Apparently, a high level of ecstasy use correlated with more aggression than might be attributable to any innate propensity for aggression. Although clinical studies have established a link between ecstasy and aggression, this is the first study to examine the presence of this link in actual behavioral outcomes. This research contributes to the growing body of evidence that undermines ecstasy's reputation as a safe drug. Data were collected from 260 ecstasy users in Atlanta, GA. Data analysis examined the likelihood of a user's engaging in aggressive behavior, controlling for key predictors of aggression independent of ecstasy use. 4 tables, 2 figures, and 63 references