Objective To observe the relationship between plasma level of homocysteine(HCY) and ischemic stroke in young and middle-aged adults,explore the clinical signficance concerning the occurrence and development of ischemic stroke in young and middle-aged adults.Methods The plasma homocysteine level of 132 young and middle-aged adults patients with ischemic and 86 control peoples were measured by means of enzymatic cycling assay.Results The plasma homocysteine level in ischemic stroke was higher than that in control group( P ＜ 0.01 ).The higher the plasma homocysteine level,the larger infarcted focus in acute ischemic stroke group of young and middleaged adults.The plasma homocysteine level and the infarcted focus was positively linearly correlated.Conclusion Hyperhomocysteinemia is a risk factor of ischemic stroke among young and middle-aged adults.The higher the plasma homocysteine level,the larger infarcted focus in acute ischemic stroke group.The plasma homocysteine level can reflect the size of the infarcted focus and the degree of disease,and the plasma homocysteine level should serve as a kind of regular examination or as an index intervention can be taken,all of which are great importance to prevent ischemic stroke and reduce its morbilily.