Two rare cases of moyamoya disease developing total occlusion of the internal carotid artery are reported. Follow up cerebral angiograms demonstrated complete occlusion of the internal carotid arteries 4 and 15 years after initial angiograms. In these clinical circumstances it appeared that the whole cerebral blood flow was supplied entirely from the external carotid circulation. It has been thought that carotid occlusion was representative of the natural history of moyamoya disease. However, progressive total occlusion of the internal carotid artery has not previously been reported in this disease. This report provides an insight that proximal occlusion is the end-point of the disease.