Adherence of erythrocytes to human umbilical vein endothelial cells (HUVEC) in patients with cerebral thrombosis and transient ischemic attack (TIA) were quantitatively studied in the flow chamber system, compared with that in healthy subjects. We found: (a) The adherence of erythrocytes to HUVEC in patients with cerebral thrombosis and TIA increased, compared with that in healthy subjects; (b) The adhesion of erythrocytes to HUVEC in patients with TIA was not significantly different from that of patients with cerebral thrombosis. These suggested that the increased adhesion of erythrocytes to endothelial cells might play an important role in the pathologic process of ischemic stroke.