Objective To investigate the frequency of thiopurine s-methyltransferase gene polymorphism and the differences between Han nationality and Uygur nationality in Xinjiang.Methods The genotype frequency of four common mutations of TPMT [TPMT * 2 (G238C),TPMT * 3A (A719G/G460A),TPMT * 3B(CA60A),TPMT * 3C(A719G)] were detected by allele specific polymerase chain reaction (AS-PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-PFLP) in healthy individuals from Xinjiang region.Results TPMT * 3 C heterozygote were found in eight individuals,in which five were Han and three were Uygur.The allele frequency of TPMT * 3 C was 2.08 ％.There was no mutation for the other three loci.Conclusion TPMT * 3 C was the most prevalent mutant in the population of Xinjiang,and its allele frequency was 2.08 ％,and there was no difference between Han and Uygur.