Early noncontrast computed tomographic scans may visualize a hyperdense middle cerebral artery before the infarct becomes visible. This sign disappears within a few days, corresponds to the clot itself, and might be associated with a poor prognosis. The aim of the study was to determine its prevalence, diagnostic value, relationship to demographic data, ability to separate embolic from nonembolic causes, short-term prognostic value, evolution over time, and relationship to arterial occlusion on angiography.