Central retinal vein occlusion is usually a disease of the elderly and is often associated with systemic vascular disease, e.g., hypertension, diabetes mellitus, arteriosclerotic vascular disease. Younger patients, especially those less than 45 years of age, with retinal vein occlusion should be evaluated carefully for the possibility of an underlying thrombotic tendency. The authors describe the ocular manifestations, pathogenesis, associated conditions, patient evaluation, and treatment of patients with central retinal vein occlusion.