The use of 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy") appears to be increasing worldwide, with "rave" attendees being one high-risk population. To date, however, only one study has collected ecstasy use information from rave attendees in the United States. To address this limitation, we collected self-report drug use information from 70 adult "club rave" attendees within the Baltimore-Washington corridor in April and May 2002. Data collection was scheduled between 12 A.M. and 5 A.M. Participation rates were high, with 85 percent of the club rave attendees completing the interview. Eighty-six percent of the respondents reported lifetime ecstasy use, 51 percent reported 30-day use, and 30 percent reported using ecstasy within the two days preceding the interview. While past-year ecstasy users were comparable to non-users with respect to a host of demographic and drug use variables, non-ecstasy users were significantly more likely than past-year users to perceive risks associated with the regular use of alcohol and ecstasy. Not surprisingly, non-ecstasy users were significantly more likely than past-year users to perceive harmful long-term physical and psychological effects associated with ecstasy ingestion. These findings suggest that rave attendees may be an important population for ecstasy-related prevention efforts.