Moyamoya disease is a rare but well described entity which has been found in the angiographic investigation of subarachnoid hemorrhage, its most common symptom in adults. We present 4 patients in whom moyamoya disease and an intracranial saccular aneurysm were discovered. In 2 of the 3 patients suffering a hemorrhage, the aneurysm was the source of bleeding. Three of the aneurysms were located at the basilar artery bifurcation. We recommend a careful search for a concomitant aneurysm in all patients with subarachnoid hemorrhage in whom moyamoya disease is found. We believe these patients should be treated as though the aneurysm were the source of bleeding.