This study sought to understand the mechanism for the increased adhesion of leucocytes and endothelial cells in ischemic stroke. 20 patients with acute cerebral thrombosis and 20 healthy subjects as controls for expression of CD11a and CD11b (adhesion molecules on surface of leucocytes) were tested in vitro by flow cytometry (FCM) method. The results showed that compared with the control group, the patient group had significantly higher rates for expression of CD11a on monocytes, granulocytes and lymphocytes (P < 0.05). The CD11b expression in the patient group was positively elevated on monocytes and granulocytes (P < 0.05), but it was of lower positive rate on lymphocytes and no statistical difference was noted between the patient and control groups. These indicate that the expression of CD11a and CD11b on leucocytes increases in cerebral ischemic damage; thus adhesion of leucocytes and endothelial cells obviously increases. This change may aggravate post-ischemic delayed neuronal death.