Ketamine is a dissociative anaesthetic that is being used in non-medical contexts. The effects of ketamine are very similar to those of phencyclidine, another dissociative anaesthetic that has enjoyed considerable popularity as a recreational drug. The effects of ketamine include analgesia, cardiovascular and respiratory stimulation, dissociation, hallucinations and anaesthesia. The potential dangers of uncontrolled ketamine use include psychosis and violence, accidents and marked psychomotor and cognitive impairment. Although studies have shown potential for tolerance to and physical dependence on ketamine, further investigation of these phenomena is needed. Ketamine is thought to produce most of its effects through antagonist activity at the PCP site of the NMDA receptor complex. Ketamine has sympathomimetic properties resulting from enhancement of catecholamine, and particularly dopamine, activity. While opioid receptor activity has been identified, this is relatively weak and the contribution to the effects of ketamine is not clear. Although much is known of the clinical uses and effects of ketamine, as yet little is understood of ketamine as a recreational drug and potential drug of dependence.