Between 1983 and 1986 the authors studied 5 patients with idiopathically dilated episcleral vessels. All of them had unilateral open-angle glaucoma (25-38 mm Hg) and elevated episcleral venous pressure (22-38 mm Hg). Orbital venography showed normal venous outflow. It is presumed that the etiological mechanism was a localized venous obstruction in the region of the extraocular muscles.