The presence of marked changes in the neural retina and retinal vessels of Long-Evans pigmented rat following bilateral carotid ligation has been previously documented by serial ophthalmologic examinations. Light and electron microscopic studies of the optic nerve in this experimental animal model revealed advanced optic nerve atrophy in ten of twelve rats examined. There was no significant pathology in either the retina or optic nerve in the remaining two rats after carotid ligation or in the sham-operated controls.