Symonds1 first stated in 1923 that the exact diagnosis of ruptured aneurysm of the circle of Willis could be made during life and gave significant clinical data to support his statement. Since then this accident has been recognized clinically with a high degree of accuracy. In addition the diagnostic criteria are now so well known that it is often possible to find old cases in which the history revealed signs and symptoms of rupture of aneurysm of the circle of Willis and the patient recovered but the physician failed to make a correct diagnosis. In such cases a diagnosis of "causes unknown" or "spontaneous subarachnoid hemorrhage" has often been made. It seems more correct, in the light of present knowledge, to assume that a leaking aneurysm of the circle of Willis was the etiologic factor. Today it is well accepted that the interval of freedom from symptoms following the