Previous studies have shown a possible association between tardive dyskinesia (TD) and debrisoquine 4-hydroxylase (CYP2D6) polymorphisms, which result in absent enzyme activity. We have recently found a positive association between TD and the CYP2D6*10 allele, which codes for the intermediate metabolizer (IM) phenotype and is characterized by decreased but not absent CYP2D6 activity in Japanese schizophrenic patients. In addition, the CYP2D6* 2 allele with the HhaI site mutation in exon 6 has also been reported to be an IM allele and a risk factor for Parkinson's disease (PD) in the Japanese population. In the present study, we investigated potential contributions of the CYP2D6*2 allele to TD using case-control and regression analysis in 99 schizophrenic patients. No significant differences in genotypic and allelic frequencies were found between patients with and without TD. Even after using regression analysis to adjust for the confounding variables, there was no significant association of the CYP2D6*2 genotype with either outcome variable, the occurrence of TD or the total AIMS score. These results suggest that the CYP2D6*2 allele may not contribute to the pathogenesis of TD.