Between 1983 and 1987 the authors studied 64 patients with dilated episcleral vessels and open-angle glaucoma. Elevated episcleral venous pressure was found to be the cause of the increased intraocular pressure. Clinically, the cause of elevation of venous pressure included spontaneous carotid cavernous fistulas, Sturge-Weber syndrome, orbital tumors, endocrine exophthalmos, anterior scleritis and idiopathic cases. A variety of pathophysiological mechanisms causing elevated episcleral venous pressure were found. The clinical course and complications associated with elevated episcleral venous pressure are discussed.