Abstract： Objective To explore the genetic interactions between angiotensin-convertingenzyme (ACE) I/D and methylenetetrahydrofolate reductase (MTHFR) C677T genotypes in middlecerebral artery stenosis (MCAS) among the asymptomatic residents in Foshan area of China. MethodsUsing a cluster sampling method, 2500 subjects were randomly selected from the residential communitiesof Rongqi town of Foshan area, Guangdong Province. By means of epidemiological questionnaire survey,physical examination, examination of the biochemical markers and transcraniai color Doppler (TCD), 897eligible subjects (306 males and 591 females) were selected from this population and subsequentlydivided into MCAS group and control group according to the TCD results. ACE and METHFR genepolymorphism analyses were conducted using amplified fragment length polymorphism-polymerase chainreaction (AFLP-PCR) and PCR-restriction fragment length polymorphism (PCR-RFLP). Chi-square test, t test, Mann-Whitney test and logistic regression analysis were used to analyze the data. ResultsGender, age, waist-to-hip ratio (WHR) and Ⅱ+CC genotype distribution in the subjects with MCAS weresignificantly different from those in the control subjects. Logistic regression analysis identified age andACE Ⅱ+ MTHFR CC genotype as the independent factors that affected MCAS. Conclusion There aregenetic interactions between ACE I/D and MTHFR C677T genotypes, and the ACE Ⅱ+MTHFR CCgenotype is an independent genetic factor for protection against MCAS in the asymptomatic residents inFoshan area of China.