We propose a clinical research project with the overall goal of applying magnetic resonance [MR} techniques to facilitate the effective and safe management of stroke. On the basis of experimental animal data we have chosen MR measures that we consider have the best probability in the shortest time of acquisition to predict, at the earliest time after onset of ischemia, the eventual development of cerebral infarction in clinical patients who suffer occlusion of a cerebral artery. At acute and subacute time points during the first 48 hours after stroke onset, we will measure the apparent diffusion coefficient of water {ADC} in patients by the use of diffusion-weighted echo planar imaging [DWI-EPI], and T2 and T2 intensity (T1) by the use of T2-weighted imaging [T2WI]. We will test the probability of tissue specific MR signatures, derived from the experimentally observed relationships of ADC and T2 to histologically graded ischemic damage, to predict he eventual development of cerebral infarction, assessed chronically at 3 months after stroke onset by the "gold standard" T2WI. To test our hypotheses, we will use Eigentool and Eigenimaging to generate tissue signature maps and quantitate volumes of stroke regions of different tissue signature at the acute, subacute an chronic time points of study. We hypothesize that, in early acute human stroke, low ADC may be associated with either eventual cellular necrosis or recovery, and therefore has a low probability of predicting cerebral infarction, but that a low ADC combined with a high T2, measured during the acute and subacute time points after stroke onset, will be the earliest probable predictor of cellular necrosis. We hypothesize also that a high ADC and high T2 combined is a marker of cellular necrosis. We believe that by the investigation of stroke patients with DWI-EPI and T2WI, it will be possible to identify reversible and irreversible components of the ischemic lesion, in which also the response of the reversible component to future cytoprotective therapy can be revealed and monitored.