The size of ruptured cerebral aneurysms in 407 cases were studied angiographically in relation to the number of times of rupture. The size of aneurysms was not influenced by the number of clinically documented episodes of bleeding. Patients with long-term clinical courses of untreated ruptured aneurysms had significantly larger aneurysms than in the general patient population. The result indicates that aneurysmal enlargement is not closely related to their rupture when considering aneurysmal growth in general. The mechanism of growth of cerebral aneurysms is discussed.