Objective:To evaluate the role of embolism in lacunar infarction(LI). Methods:Consecutive patients admitted to our hospital with acute cerebral infarction from Oct. 2008 to Jun. 2011 were reviewed. Patients with cardioembolism or other determined etiologies were excluded while other patients were divided into two groups,including the LI group and the non-LI group according to the diameter of infraction. Risk factors and arteries plaques and stenosis of two groups were analyzed. Results:There was no statistical difference of every risk factor between two groups(P > 0.05);the plaques and stenosis in the territory arteries were significantly more frequent than that in the contralateral side in both groups(P < 0.05);the plaques and stenosis in the territory arteries and the progressive and multiple infraction were significantly less frequent in the LI group than in the non-LI group (P < 0.05);the differences of plaques and stenosis in the territory arteries of progressive infraction and plaques of multiple infraction between two groups were of no significance(P > 0.05),but stenosis in the territory arteries of multiple infraction was significantly less frequent in the LI group than in the non-LI group (P < 0.05). Conclusion:Embolism is an important but not dominant mechanism in lacunar infarction.