The criteria of the cerebrovascular Moyamoya disease is defined by the characteristic findings of its cerebral angiograms, as follows; 1) The internal carotid siphon is narrowed or obstructed bilaterally. 2) The "Moyamoya vessels" are observed at the base of the brain or the basal ganglionic regions. 3) Main trunks of the cerebral arteries such as the anterior, the middle, and/or the posterior cerebral arteries are often not or poorly visualized. 4) Its etiology is unknown. It has been known that the occlusion of the internal carotid fork with Moyamoya vessels is not infrequently seen in patients with tuberculous meningitis, sickle cell anemia, head trauma, and so on. In the definition of the disease, patients with known etiology and/or unilateral occlusion in the carotid fork must be excluded. However, the cases who cannot fulfil its criteria of the cerebrovascular Moyamoya disease, but have its characteristic Moyamoya vessels and collateral pathways have been reported. We investigated the findings of cerebral computed tomograms in 13 patients who did not fulfil the criteria of the cerebrovascular Moyamoya disease, but revealed the Moyamoya vessels. The subjects are 5 males and 8 females, ranging 15 to 70 years old. The past histories of 9 patients among them revealed hypertension, radiation therapy for pituitary adenoma, head trauma, aplastic anemia, and the Raynaud phenomenon. By angiographic evaluations, occlusions in the unilateral carotid forks were seen in 7 patients, and stenoses in those were in 5 patients. One patient showed only a severe stenosis in the horizontal portion of the middle cerebral artery.(ABSTRACT TRUNCATED AT 250 WORDS)