A range of studies has indicated that users of 3.4-Methylene-dioxymethamphetamine (MDMA, 'Ecstasy') display cognitive deficits, particularly memory impairment, as compared to non-drug using controls. Yet it is difficult to determine whether these deficits are caused by MDMA or some other confounding factor, such as polydrug use. The present study was designed to establish the direct relation between MDMA and memory impairment under placebo-controlled conditions. Eighteen recreational MDMA users participated in a double blind, placebo controlled, 3-way crossover design. They were treated with placebo, MDMA 75 mg and methylphemidate 20 mg. Memory tests were conducted between 1.5-2 h (intoxication phase) and between 25.5-26 h (withdrawal phase) post dosing. Results showed that a single dose of MDMA caused impairment of immediate and delayed recall on a verbal learning task during the intoxication phase. However, there was no residual memory impairment during the withdrawal phase. Subjects reported more fatigue and less vigour, but no symptoms of depression during the withdrawal phase of MDMA treatment. Methylphenidate did not affect memory or mood at any time of testing. A single dose of MDMA produces transient memory impairment.