Central nervous system involvement of Behcet's disease (BD) shows various neuropsychiatric manifestations. The differential diagnosis may include many other systemic or neurologic diseases. Moyamoya disease (MD) is a progressive cerebrovascular occlusive disease of unknown etiology with a high incidence in Korea and Japan. HLA-B51 is significantly associated with both MD and BD. We first report a case of BD associated with MD in a 32-year-old woman with transient ischemic attacks of left hemiparesis and episodic dizziness. She was diagnosed as having BD manifested with oral ulcer, genital ulcer, erythema nodosum and positivity of pathergy reaction and HLA-B51. There was no evidence of cerebral infarction or hemorrhage in brain MRI. MR angiogram and 4-vessel angiography showed occlusion of bilateral internal carotid arteries and the development of collateral circulation, suggestive of MD. Bypass surgery was successfully performed. When evaluating the manifestations of MD, a chronic inflammatory disease, such as BD, needs to be considered as the underlying disease, especially in prevalent area of both diseases.