In this paper, the authors report biplane computed cerebral angiotomographic findings in 5 cases of Moyamoya disease. The specific features of Moyamoya disease on the CT image were as follows: On the axial plane, the linear structures of the anterior half of the circle of Willis and the proximal portion of the middle cerebral arteries disappeared, and instead of these normal structures, irregular, tortuous or patchy high-density areas just like a "caterpillar" were shown in the basal cistern and medial Sylvian fissures. On the modified coronal plane, the supraclinoid internal carotid arteries and the carotid fork could be identified only with a difficulty, and abnormal, "nebular" high-density areas consisting of irregular, tortuous or patchy high-density vascular components became visible in the basal cistern extending to the basal ganglia. A modified coronal plane and intravenous minimum dose bolus injection method seemed to be more useful for the visualization of these specific features on the CT image. Even before carotid angiography, we can suspect Moyamoya disease for finding these specific features on the CT image. Carotid angiography has been the only method of diagnosing Moyamoya disease. Instead of this invasive examination, computed cerebral angiotomography is useful in detecting Moyamoya disease conveniently and non-invasively. Therefore, we may conclude that computed cerebral angiotomography is very useful method for screening and follow up study of Moyamoya disease.