Aim To investigate the relationship between platelet and cerebral infarction as well as carotid atherosclerosis. Methods Positive rates of PAC-1 and CD62P,which are both platelet membrane glycoproteins,were measured by flow cytometry in blood samples while carotid artery were evaluated by color Doppler ultrasound in 75 patients with atherosclerotic cerebral infarction and 61 healthy examination persons. Results Positive rates of PAC-1 and CD62P in the cerebral infarction groups no matter with or without carotid atherosclerosis were significantly higher than that in the corresponding control groups. In addition,the positive rates in the groups with carotid atherosclerosis were significantly higher than those in the groups without carotid atherosclerosis both in cerebal infarction groups and in control groups. Farthermore,the positive rates in the groups of cerebral infarction with carotid atherosclerosis were the highest. Conclusion The level of platelet activation is associated with cerebral infarction and carotid atherosclerosis. Activating platelet may play an important role in atherosclerotic cerebral infarction.