Aim To investigate the relationship between plasma homocysteine(Hcy),polymorphisms of the methylenetetrahydrofolate reductase(MTHFR) gene and atherosclerotic cerebral infarction. Methods Plasma Hcy,polymorphisms of the MTHFR gene in 68 patients with atherosclerotic cerebral infarction(CI) and 50 controls were measured by fluorescence polarization immunoassay(FPIA) and polymerase chain reaction and restriction fragment length polymorphism(PCR-RFLP) respectively. Results The frequencies of TT genotype and T allele were significantly higher in CI group than in controls(P><0.05).Plasma Hcy levels was significantly higher in CI group than in controls(P><0.05).The homocysteine concentration was significantly higher in TT genotype than CT and CC genotypes both in CI group and in control group(P><0.05). Conclusion Elevated Hcy levels is a risk factor for atherosclerotic cerebral infarction.MTHFR C677T polymorphism was significantly related to plasma Hcy levels and atherosclerotic cerebral infarction.