Demographic information, drug use parameters and treatment outcome variables were recorded for 350 people admitted for treatment of methamphetamine abuse in the Los Angeles (CA) area, with analyses comparing those methamphetamine users who also reported ecstasy use with those who did not report any ecstasy use. 20% (70/350) reported having used ecstasy at least once. Age of first ecstasy use was 21.8 years (range = 13-38 years). About half of the sample had used ecstasy for a year but no longer used it (49% of 70). Duration of use ranged from a year (12 months) to 30 years (360 months). 28% of ecstasy-using methamphetamine users reported times when they used ecstasy for 3 or more days a week. In this sample, ecstasy using methamphetamine users were younger, had fewer children, were more likely to have same sex sexual partners, took a greater number of drugs, had higher incomes and were less likely to complete treatment than were non-ecstasy using methamphetamine users. While ecstasy-using methamphetamine users did not differ from non-ecstasy uses in severity of methamphetamine dependence, they were more likely to relapse 24 months (2 years) after treatment. Ecstasy-using methamphetamine users entered substance-abuse treatment at a younger age than those reporting no ecstasy use. Injection drug use was more prevalent methamphetamine users who used ecstasy, and they were more likely to receive inpatient treatment. However, neither of these factors remained significantly different across groups after performing an exploratory factor analysis. The association between ecstasy use and failure to complete treatment was not explained by other associated variables, such as income or use of other drugs, since removing ecstasy use from the model significantly weakened its predictive value. Overall, the authors note that the profile of ecstasy-using methamphetamine users matches that of a polydrug user profile. They acknowledge that their sample is not representative of the general population of ecstasy users.