The present study provides a profile of acquisition and maintenance of self-administration of +/-3,4-methylenedioxymethamphetamine (MDMA) obtained from a large cohort of rats tested during a 2 year period. Of the 128 rats, 49% self-administered 1.0 mg/kg/infusion MDMA to an initial criterion within a 25 day cutoff period. The number of test sessions required to meet this initial criterion was normally distributed around an average of 15.9 days and responding increased in a compensatory manner when the dose was decreased. In a subgroup of rats that self-administered MDMA for an additional 14 days intake increased from 8.5 to 15.25 mg/kg/day. Thus, under these conditions, MDMA is a reliable reinforcer for about half of a large sample of rats, responding is dose-dependent and acquisition of self-administration for these sensitive rats requires more test sessions than is typically used for studies examining self-administration of other drugs of abuse.