BACKGROUND AND PURPOSE There are few studies analyzing stroke in women, taking into account the vascular risk factors, cause of stroke, clinical picture, and outcome. The purpose of this study was to analyze possible sex differences in patients suffering first-ever acute stroke. METHODS From December 1995 to January 2002, 1581 patients with first-ever acute stroke were analyzed, taking into account sex, age, risk factors, clinical presentation, stroke subtype, treatment, and outcome data. RESULTS Mean age was higher in women than in men (P<0.001). Hypertension (P=0.0027) and cardioembolic disease (P=0.0035) were independent factors related to women. Alcohol overuse (P<0.001), smoking (P<0.001), and vascular peripheral disease (P=0.031) were related to the male sex. Women more often suffered aphasic disorders (P<0.001), visual field disturbances (P<0.05), and dysphagia (P<0.01) than men. There were no differences in hemorrhagic and ischemic strokes according to sex. Women suffered more cardioembolic strokes (P<0.001); men suffered more atherothrombotic (P<0.001) and lacunar strokes (P<0.05). Women who survived remained more disabled than men (P<0.001). CONCLUSIONS Sex determines some clear differences in patients suffering a first-ever stroke. Women were, on average, 6 years older than men and had a different profile of vascular risk factors and a different distribution of stroke subtypes. Women had a longer hospital stay and remained more disabled than men. The amelioration of hypertension control and increase in anticoagulant treatment in patients with atrial fibrillation would be the best options for preventing stroke, especially in women.