Among 86 patients with aneurysms arising from the vertebral artery or its branches, 24 had dissecting aneurysms. The patients with dissecting aneurysms were characteristically relatively young males. Twenty-one patients presented with subarachnoid hemorrhage (SAH) and three with ischemia. Severe headache or neck pain occurred in all three patients with ischemia. Five of the 21 patients with SAH and all three patients with ischemia experienced recurrent episodes. Angiography typically showed fusiform dilatation and proximal and/or distal narrowing of the affected artery. The difficulty of diagnosing this disorder is pointed out. Surgery was performed in 19 patients, the most common technique being clip-occlusion of the proximal vertebral artery. There were no postoperative deaths or rebleeding; a lateral medullary syndrome developed in three patients. The observation at surgery of intramural clot with characteristic discoloration was limited to the cases operated on within 36 days after the ictus. After this period, the aneurysm was whitish gray in color and had become firm. Of 36 other cases of vertebral dissecting aneurysm reported in the literature, 20 were operated on. The indications for surgery are discussed.