Whole blood samples from 50 unrelated Korean subjects were genotyped for 3kb of 5' upstream region, all exon-intron boundaries, exons, and UTR regions of CYP2C8 gene by direct sequencing. Genotyping of CYP2C8 has been addressed only for null allelic variant, CYP2C8*11 using pyrosequencing in the 447 Koreans, 93 African-Americans, 100 Caucasians, 348 Chineses and 100 Vietnameses. Then, in-vivo single PK study of CYP2C8 probe, rosiglitazone(4mg), was conducted in 7 healthy subjects with CYP2C8*1/*1 and 2 with CY2C8*1/*11.