Thrombolysis is an effective but potential deleterious therapy and should therefore be limited to patients with acute intracerebral vessel occlusion and salvageable tissue. MRI currently develops towards the new diagnostic standard for the selection of stroke patients eligible for acute thrombolytic treatment and acute stroke studies. Diffusion-and perfusionweighted MRI provides diagnostic information not available from neurological assessments or from CCT and conventional spin-echo MRI. As high-speed DWI and PWI protocols become standardized, a 15-min integrated stroke protocol of employing echo-planar imaging (EPI) can be routinely performed in the setting of acute clinical stroke. The combination of these MR techniques is suitable to define tissue at risk of infarction that is potentially salvageable brain tissue (an estimate of the ischemic penumbra) and may respond to early recanalization even beyond 3 h after stroke onset. The extension of the therapeutic window for thrombolytic therapy towards 6 h in a subpopulation of acute stroke patients might open the way for the successful reperfusion therapy in more stroke patients.