Male Wistar rats were administered either (a) a high dose regime of 3,4-methylenedioxymethamphetamine (MDMA) (4 x 5 mg/kg, i.p. over 4 h on each of 2 consecutive days), (b) a moderate dose regime of MDMA (1 x 5 mg/kg on each of 2 consecutive days), (c) D-amphetamine (4 x 1 mg/kg over 4 h on each of 2 days), or (d) vehicle injections. The high MDMA dose regime and the amphetamine treatment both produced acute hyperactivity and hyperthermia. Twelve weeks later, all rats were tested in the drug-free state on a battery of anxiety tests (elevated plus maze, emergence and social interaction tests). A further 2 weeks later they were tested on a novel object recognition memory task. Rats previously given the neurotoxic dose of MDMA showed greater anxiety-like behaviour on all three anxiety tests relative to both controls and D-amphetamine-treated rats. Rats given the moderate MDMA dose regime also showed increased anxiety-like behaviour on all three tests, although to a lesser extent than rats in the high dose group. In the object recognition task, rats given the high MDMA dose regime showed impaired memory relative to all other groups when tested at a 15-min delay but not at a 60-min delay. Rats previously exposed to amphetamine did not differ from saline controls in the anxiety or memory tests. These data suggest that moderate to heavy MDMA exposure over 48 h may lead to increased anxiety and memory impairment 3 months later, possibly through a neurotoxic effect on brain serotonin systems.