The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.