OBJECTIVE: To assess whether 5, 10-methylenetetrahydrofolate reductase (MTHFR) gene poly-morphism (TT genotype or T allele) is a risk factor for ischemic cerebrovascular disease (ICVD). DATA SOURCES: MEDLINE and PubMed databases from September 1997 to December 2009 were searched for case-control studies that examined MTHFR genotype in human ICVD using “MTHFR, gene, polymorphism, and ischemic cerebrovascular disease” as search key words. STUDY SELECTION: Eighteen associated studies were identified. The methods used to collect relevant information factors were similar between case and control groups, and diagnosis of ischemic cerebrovascular disease was in accordance with Trial of ORG 10172 in Acute Stroke Treatment criteria classification, with some referring to European Stroke Diagnostic Criteria. Quality of all included studies was evaluated, and meta-analysis was conducted using RevMan4.2 software (Cochrane Collaboration, http://www.cochrane-handbook.org) following strict screening. MAIN OUTCOME MEASURES: The correlation between MTHFR gene TT genotype or T allele and ICVD was determined. RESULTS: Eighteen studies involving 4 295 patients with ICVD and 6 169 control subjects were included for this meta-analysis. There was a significant difference in MTHFR gene TT genotype or T allele frequency (χ2 = 15.737, 9.186, P < 0.01) between ICVD cases and controls. In addition, six Chinese Han population studies were specially reviewed by meta-analysis. Results showed no sig-nificant difference between ICVD and control groups with regard to frequency of MTHFR gene TT genotype and T allele (χ2 = 1.076, 2.434, P > 0.05) in the Chinese Han population. CONCLUSION: Results from the present meta-analysis suggested that the MTHFR gene TT genotype or T allele is a risk factor for ICVD. However, the TT genotype or T allele is not a risk factor for ICVD in the Chinese Han population. OBJECTIVE: To assess whether 5, 10-methylenetetrahydrofolate reductase (MTHFR) gene poly-morphism (TT genotype or T allele) is a risk factor for ischemic cerebrovascular disease (ICVD). DATA SOURCES: MEDLINE and PubMed databases from September 1997 to December 2009 were searched for case-control studies that examined MTHFR genotype in human ICVD using “MTHFR, gene, polymorphism, and ischemic cerebrovascular disease ” as search key words. STUDY SELECTION: Eighteen associated studies were identified. The methods used to collect relevant information Factors were similar between case and control groups, and diagnosis of ischemic cerebrovascular disease was in accordance with Trial of ORG 10172 in Acute Stroke Treatment criteria classification, with some referring to European Stroke Diagnostic Criteria. Quality of all included studies was evaluated, and meta- analysis was conducted using RevMan4.2 software (Cochrane Collaboration, http://www.cochrane-handbook.org) following strict screening . MAIN OUTCOME MEASURES: The correlation between MTHFR gene TT genotype or T allele and ICVD was determined. RESULTS: Eighteen studies involving 4 295 patients with ICVD and 6 169 control subjects were included for this meta-analysis. There was a significant difference in MTHFR In addition, six Chinese Han population studies were specifically reviewed by meta-analysis. Results showed no sig-nificant difference between ICVD and control groups with regard to frequency of MTHFR gene TT genotype and T allele (χ2 = 1.076, 2.434, P> 0.05) in the Chinese Han population. CONCLUSION: Results from the present meta-analysis suggested that the MTHFR gene TT genotype or T allele However, the TT genotype or T allele is not a risk factor for ICVD in the Chinese Han population.