This study describes the lifetime prevalence, correlates, and age of onset of selected psychiatric disorders among a community sample of MDMA users (n = 402), aged 18 to 30, in Ohio. Participants responded to interviewer-administered questionnaires, including sections of the computerized Diagnostic Interview Schedule for DSM-IV. Fifty-five percent of the sample had at least one lifetime disorder, with major depression (35.3%) and antisocial personality disorder (ASPD) (25.4%) the most common. Proportionately more women were diagnosed with depression, generalized anxiety disorder, and posttraumatic stress disorder (PTSD), while proportionately more men were diagnosed with ASPD. Proportionately more non-White participants had attention deficit/hyperactivity disorder (AD/HD). Higher levels of education were associated with proportionately less PTSD, ASPD, and AD/HD. Higher frequencies of MDMA use were associated with proportionately more ASPD and AD/HD. Comparing the age of first MDMA use with the age of onset for selected psychiatric disorders revealed that for most participants disorders preceded use. Multivariate analysis revealed participants with more than a high school education were less likely to have experienced a lifetime disorder, while those who had used MDMA more than 50 times were more likely. Variations in the prevalence of psychiatric disorders have practical implications for drug abuse prevention and treatment programs.