Pioglitazone is a thiazolidinedione antihyperglycaemic drug with insulin-sensitizing properties.We investigated the frequencies of CYP2C8 and CYP2C9 genetic polymorphisms in Chinese population, and whether these variant genotypes influence pharmacokinetic phenotype of substrate pioglitazone.Single nucleotide polymorphisms (SNPs) were determined by the PCR-RFLP method in 244 Chinese Han healthy subjects.After a single oral dose of 30 mg pioglitazone, the plasma concentrations of parent drug and two major active metabolites M-Ⅲ and M-Ⅳ were measured using a validated LC-MS/MS in 21 of these 244 volunteers.The results showed that unique frequencies of CYP2C8*2 (0.0%), CYP2C8*3 (0.0%) and CYP2C9*2 (0.0%) alleles were significantly different from that reported in Caucasians and Africans, and there were only 10 variant CYP2C9*1/*3 heterozygous (CYP2C9*3 carriers) among 244 Chinese subjects.