Objective To investigate the correlation between the plasma homocysteine(Hcy) level and the plaque and its degree of the carotid atherosclerosis (CAS) in elderly patients with acute cerebral infarction (ACI).Methods 93 definit ACI patients recieved the colour Doppler ultrasonograph to detect the intima-media thickness (IMT) of bilateral carotid arteries. Then, the patients were divided into group with CAS plaque(60 cases) and group without CAS plaque(33 cases) according to the result of the detection. Also the degree of CAS were divided to 0～4 levels. The concentration of plasma Hcy of all the patients were measured by enzymatic cycling assay. The correlation analysis was made between plasma Hcy levels and the CAS plaque and the degree of CAS.Results The concentration of plasma Hcy in the group with CAS plaque[18.83 (15.20～24.03)?mol/L] was significantly higher than that in group without CAS plaque[12.30 (9.70～15.10) ?mol/L](P