Chronic administration of typical antipsychotic agents, which mainly act on the dopamine receptors, implicates a role of dopamine system on the susceptibility of tardive dyskinesia (TD). In the present study, the association between a functional Val158Met polymorphism of Catechol-O-methyltransferase (COMT) gene and TD occurrence and TD severity was investigated in 299 Chinese schizophrenic patients with long-term antipsychotic treatment (TD: 166, non-TD: 133). After adjusting the effects of confounding factors, there was no significant association between COMT genotype and TD occurrence (p=0.367). Among TD patients, we found no significant correlation between COMT genotypes and the total scores of abnormal involuntary movement scale (AIMS) (p=0.629). We concluded that this COMT polymorphism might not play a major role in the susceptibility of TD nor on the severity of TD.