BACKGROUND AND PURPOSE: Early and accurate assessments of cerebral ischemia allow therapy to be tailored to individual stroke patients. We examined the feasibility of using a novel method for measuring cerebral blood flow (CBF) of ischemic tissue based on MRI after middle cerebral artery occlusion (MCAO). Moreover, the regional correlations between CBF and cerebral blood volume (CBV) were investigated in the regions with acute ischemic stroke. METHODS: CBF and CBV were measured before and after MCAO or reperfusion by positron emission tomography (PET) in 13 pigs. Just after the PET scans, CBF and CBV were measured by MR bolus tracking and were compared with results obtained by PET at 6 hours after permanent MCAO or reperfusion. The infarction was verified histologically. RESULTS: The MR method yielded parametric CBF and CBV maps with tissue contrast in good agreement with parametric PET images, which demonstrated hypoperfused and hyperperfused areas after MCAO or reperfusion. Both MRI and PET technology showed that CBF values below 60% of the contralateral value induced a reduction of CBV, which committed the tissue to infarction. CONCLUSIONS: The novel MR method provides accurate measurement of CBF and CBV in acute stroke and hence gives useful information for planning the appropriate therapeutic intervention.