AIM: To study the relationship of P450 2C9 genetic polymorphisms and the pharmacokinetics oftolbutamide in Chinese.METHODS: P450 2C9 genotype was determined by oligenucleotide rnicroarray.Using tolbutamide as a probe of P450 2C9 activity, P450 2C9 phenotype in 63 healthy individuals expressing the P450 2C9*1/*1,*1/*3 and *3/*3 genotypes were evaluated.