MDMA or 'ecstasy' (3,4-methylenedioxymethamphetamine) is a commonly used psychoactive drug that has unusual and distinctive behavioral effects in both humans and animals. In rodents, MDMA administration produces a unique locomotor activity pattern, with high activity characterized by smooth locomotor paths and perseverative thigmotaxis. Although considerable evidence supports a major role for serotonin release in MDMA-induced locomotor activity, dopamine (DA) receptor antagonists have recently been shown to attenuate these effects. Here, we tested the hypothesis that DA D 1 , D 2 , and D 3 receptors contribute to MDMA-induced alterations in locomotor activity and motor patterns. DA D 1 , D 2 , or D 3 receptor knockout (KO) and wild-type (WT) mice received vehicle or ( + /À)-MDMA and were tested for 60 min in the behavioral pattern monitor (BPM). D 1 KO mice exhibited significant increases in MDMA-induced hyperactivity in the late testing phase as well as an overall increase in straight path movements. In contrast, D 2 KO mice exhibited reductions in MDMA-induced hyperactivity in the late testing phase, and exhibited significantly less sensitivity to MDMA-induced perseverative thigmotaxis. At baseline, D 2 KO mice also exhibited reduced activity and more circumscribed movements compared to WT mice. Female D 3 KO mice showed a slight reduction in MDMA-induced hyperactivity. These results confirm differential modulatory roles for D 1 and D 2 and perhaps D 3 receptors in MDMA-induced hyperactivity. More specifically, D 1 receptor activation appears to modify the type of activity (linear vs circumscribed), whereas D 2 receptor activation appears to contribute to the repetitive circling behavior produced by MDMA.