AIM:To investigate the possible association of microsomalepoxide hydrolase (mEH) Tyr113 His polymorphism withsusceptibility to esophageal squamous cell carcinoma (ESCC)in a population of North China.METHODS:The mEH Tyr113 His genotypes were determinedby polymerase-chain reaction (PCR)-restriction fragmentlength polymorphism (RFLP) analysis in 257 patients withesophageal squamous cell carcinoma (ESCC) and 252 healthysubjects as a control group.RESULTS:The frequencies for Tyr and His alleles were44.2 %,55.8 % in ESCC patients,and 44.0 % and 56.0 %in healthy subjects,respectively.No statistic difference inallele distribution was observed between ESCC patients andcontrols (χ~2=0.008,P=0.929).The overall genotype distributiondifference was not observed between cancer cases andcontrols (χ~2=2.116,P=0.347).Compared with Tyr/Tyrgenotype,neither His/His genotype nor in combination withTyr/His genotype significantly modified the risk of thedevelopment of ESCC,the adjusted odds ratio was 1.076(95 % CI=0.850-1.361) and 0.756 (95 % CI=0.493-1.157),respectively.When stratified for sex,age,smoking statusand family history of upper gastrointestinal cancer,His/Hisgenotype alone or in combination with Tyr/His genotypealso did not show any significant influence on the risk ofdeveloping ESCC..CONCLUSION:MEH Try113his PolymorPhism may not beused as a strati6cation marker in screening individuals atah igh risk of ESCC AIM: To investigate the possible association of microsomalepoxide hydrolase (mEH) Tyr113 His polymorphism with susceptibility to esophageal squamous cell carcinoma (ESCC) in a population of North China. METHODS: The mEH Tyr113 His genotypes were determined by polymerase-chain reaction (PCR) The frequencies for Tyr and His alleles were 44.2%, 55.8% in ESCC patients, and 44.0% and 56.0% respectively. The results of fragment length polymorphism (RFLP) analysis in 257 patients with withesophageal squamous cell carcinoma (ESCC) and 252 health subjects as a control group in healthy subjects, respectively. No statistic difference inallele distribution was observed between ESCC patients and controls (χ ~ 2 = 0.008, P = 0.929). The overall genotype distribution difference was not observed between cancer cases and controls (χ ~ 2 = 2.116, P = ) .Compared with Tyr / Tyrgenotype, neither His / His genotype nor in combination with Tyr / His genotype significantly modified the risk of the development of ESCC, the adjusted odds ratio was 1.076 ( 95% CI = 0.850-1.361) and 0.756 (95% CI = 0.493-1.157), respectively. Stratified for sex, age, smoking status and family history of upper gastrointestinal cancer, His / Hisgenotype alone or in combination with Tyr / His genotypealso did not show any significant influence on the risk of developing ESCC..CONCLUSION: MEH Try113his PolymorPhism may not beused as a strati6cation marker in screening individuals atahigh risk of ESCC