Moyamoya disease is an unusual form of chronic cerebrovascular occlusive disease characterized usually by bilateral stenosis of distal internal carotid arteries and their vicinity, by a hazy network of collateral circulation at the base of the brain called moyamoya vessels and clinically by recurring hemispheric ischemic attacks in children. This disease was first reported by a Japanese neurosurgeon and many reports and studies on this disease have been published in Japan. We report here the recent progress in the diagnosis of the disease and introduce a newly developed operative procedure which we think is an ideal surgical method for treating this disease in children.