BACKGROUND AND PURPOSE: Takayasu's arteritis is a nonspecific arteritis involving major cerebral arteries. The aim of our study is to examine cerebral hemodynamics and metabolism in Takayasu's arteritis with neurologic symptoms. METHODS: We measured cerebral blood flow and metabolism using positron emission tomography in seven patients (14 to 59 years of age) with Takayasu's arteritis who developed transient ischemic attacks (2 patients), ischemic stroke (4) or putaminal hemorrhage with multiple brain infarction (1). RESULTS: All patients had severe stenosis or occlusion of one or more major cerebral arteries. There were no significant differences in the values of cerebral blood flow, oxygen extraction fraction, and cerebral blood volume in the infarcted and noninfarcted hemisphere. By contrast, the value of cerebral metabolic rate for oxygen in the infarcted hemisphere was markedly reduced (1.87 mL/100 mL per minute, P < .01) compared with controls. Mean transit time in the infarcted hemisphere was significantly greater than in the noninfarcted one, both in patients and controls (P < .01 and P < .05, respectively). CONCLUSIONS: Collateral blood flow to the hemisphere without brain damage may be relatively well developed in Takayasu's arteritis, although hemodynamic reserve as well as oxygen metabolism were impaired in the infarcted hemisphere with ischemic lesions.