Moyamoya disease is a rare occlusive cerebrovascular disease characterized by stenosis or occlusion of the main cerebral arteries. It has a tendency for multifactorial inheritance and familial occurrence, although its pathogenesis is not clear. We observed this disease in two girls from the same family:one was eight years old and the other was 45 months. They presented with transient ischemic attacks. We performed cerebral angiography on both patients and magnetic resonance angiography (MRA) on the younger. Both approaches showed the typical features of moyamoya disease, and MRA successfully revealed abnormal findings specific for the disease in the second child. Both children received encephaloduroarteriosynangiosis (EDAS) and this produced good results. MRA is thus a powerful and noninvasive way of detecting individuals at high risk of developing this disease. Considering the reported familial incidence of moyamoya disease in Japan, a careful search for family members using MRA would probably reveal many more such cases in Korea.