Cytochrome P450 2C9 (CYP2C9) shows genetic polymorphism with high interethnic variation, but no report has addressed the genetic polymorphism in the Vietnamese population. In the present study, the distribution of 2 common allelic variations of CYP2C9 was investigated in Vietnamese Kinh population, a major ethnic group in Vietnam. Genomic DNA from 157 Vietnamese subjects was amplified by polymerase chain reaction, and the presence of CYP2C9*2 and CYP2C9*3 allelic variants was determined by pyrosequencing. Among 157 Vietnamese subjects, no subject with the CYP2C9*2 allele was detected, but 7 subjects were heterozygous for the CYP2C9*3 allele. The allele frequency of CYP2C9*3 was 2.2% in the Vietnamese Kinh population. This genotype distribution was well correlated with previous reports suggesting no occurrence of CYP2C9*2 in Asians. These results suggest that CYP2C9*2 may be absent in Vietnamese Kinh population and that CYP2C9*3 is major allelic variant that causes interindividual variation of drug responses to CYP2C9 substrate drugs in the Vietnamese Kinh population.