The cannabis constituent cannabidiol has been suggested to have the properties of an atypical antipsychotic. Previous work in our laboratory has demonstrated that cannabidiol reverses deficits in sensorimotor gating induced by the NMDA receptor antagonist MK - 801. The present study aimed to investigate the effect of cannabidiol on MK - 801 - induced social withdrawal in rats,an animal model of negative symptoms associated with schizophrenia. Separate groups of rats were treated with MK - 801 (0.3 mg/kg) following pre - treatment with cannabidiol (5 mg/kg) or clozapine (3 mg/kg). Rats were placed in an open arena and videotaped for 10 min and social and locomotor behaviour was assessed. MK-801 produced a decrease in social behaviours such as investigation,following and climbing over. Cannabidiol reversed this decrease and reinstated social interaction to a similar level to control. Clozapine decreased locomotor activity and did not reverse social withdrawal,perhaps due to the hypomotility. These results support the evidence for the potential antipsychotic properties of cannabidiol.