Cytochrome P450 2D6 (CYP2D6) is an important hepatic microsomal enzyme. CYP2D6 is expressed not only in the liver but also in the central nervous system, especially the midbrain. CYP2D6 is involved in metabolizing many anti psychotic agents and were suggested to be associated with some complex diseases. The present study aimed to explore whether there is any association between CYP2D6 alleles and schizophrenia susceptibility in patients. CYP2D6 alleles and genotype frequencies have been evaluated in 88 Chinese schizophrenic patients (40 men and 48 women, aged 40.38 +/- 13.45 years) and in 93 healthy controls (40 men, 53 women, aged 43.60 12. 05 years). There is no statistically significant difference in the genotypes and allele frequencies of CYP2D6 ( C100T) between schizophrenics and healthy controls (P > 0.05). Our results indicate that CYP2D6 ( C100T) polymorphism is unlikely to represent a major risk factor in susceptibility to schizophrenia.