Objective\ To study the relationship between the pathogenesis of vascular dementia(VD) and the ultrastructural character of blood\|brain barrier(BBB) in the caudatolenticulum.\ Methods\ The ultrastructure of BBB in caudatolenticulum of 10 rats of which 5 rats bilateral common carotid arteries were occluded and 5 rats as control group.\ Results\ The outline of some basement membranes of capillaries in VD rats was unclear, thicker and has uneven density.\ There were myelinic materals outside some basement mem...