Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are new magnetic resonance imaging (MRI) technologies, and the former has been widely accepted for the early detection and evaluation of hemodynamic status of acute cerebral infarction, which the latter evaluates for further improvement. In this study we aimed to know the clinical usefulness of detecting the penumbra zone surrounding subcortical infarction using DWI and PWI. Twelves patients with acute cerebral ischemia were imaged with DWI, PWI, and magnetic resonance angiogram (MRA) within 48 hours of onset. We compared lesion size on DWI with that on PWI using mean transit time (MTT) map. Comparisons were made between infarct volumes measured by DWI and PWI, and between cortical areas on infarcted side and on non-infarcted side using time-to-peak delay. Non-infarcted cortical areas of both hemisphere were analysed by time-to-peak (TTP) delay pattern using PWI, and then were compared one with the other hemisphere in TTP. Also the bilateral vascular status were analysed on the basis of MRA. Out of 12 patients, 6 had larger lesion on PWI than on DWI (Group 1), and the rest had the same or smaller lesion on PWI (Group 2). In Group 1, TTP delay (mean: 5 sec, p<0.004) and neurologic disability (p<0.05) were greater. Patency of artery in infarcted areas correlated well with TTP delay pattern on PWI (p<0.01). Although this is a preliminary study with a small population, it suggests that the presence of diffuse penumbra zone around the cerebral infarction poses higher risk of neurological disability. This study indicates that PWI is useful to predict subsequent outcome in subcortical infarction.