The ocular ischemic syndrome is a manifestation of chronic vascular insufficiency. The natural history is for progressive visual loss. The authors describe 12 patients (13 eyes) who presented with at least one asymmetric ocular finding, including midperipheral dot and blot hemorrhages (hypoperfusion retinopathy) (in 8), iris neovascularization (in 7), neovascular glaucoma (in 3) and vitreous hemorrhage (in 1). Cerebral angiography revealed stenosis or occlusion of the ipsilateral carotid artery in all cases. The treatment was panretinal photocoagulation (in four cases), cerebrovascular surgery (in three) or both (in six). All but one patient showed stabilization of visual acuity (20/60 or better in nine cases) and regression of proliferative retinopathy and of iris neovascularization. The results underline the importance of early recognition and treatment of the ocular ischemic syndrome.