Background and Purpose-The purpose of this study was to evaluate the value of the initial arterial study as a predictor of 90-day mortality in patients with acute ischemic stroke. Methods-A total of 1220 unselected patients assessed during the first 24 hours after stroke onset were prospectively studied. Initial stroke severity was evaluated by the National Institutes of Health Stroke Scale and dichotomized in mild (National Institutes of Health Stroke Scale Յ7) and severe (National Institutes of Health Stroke Scale Ͼ7). Severe arterial stenosis (Ն70%) or arterial occlusion in the symptomatic territory was determined by a Doppler study and also by additional explorations (carotid duplex, MR or CT angiography) in the first 24 hours after admission. The following variables were also analyzed: age, gender, previous functional status, smoking, hypertension, hyperlipidemia, diabetes mellitus, peripheral arterial disease, ischemic heart disease, heart failure, atrial fibrillation, previous stroke, and prior use of antithrombotic or statins. Ninety-day mortality was the end point of the study. Results-Ninety-day mortality was 15.7%. A total of 25.5% of all deaths were in patients with mild stroke. In addition to well-known factors related to mortality (age, stroke severity, ischemic heart disease, heart failure, and previous disability), severe arterial stenosis/occlusion was the factor with the highest relationship with 90-day mortality (adjusted OR: stenosis 2.13, occlusion 4.42, both 3.36). Arterial stenosis/occlusion was a higher predictor of 90-day mortality in patients with mild (adjusted OR: 5.38) than severe stroke (adjusted OR: 3.05). Conclusions-Severe arterial stenosis/occlusion in the early arterial study was highly related with 90-day mortality in an unselected series of patients with stroke. These data achieve special relevance in patients with initial mild stroke.