Objective: To delineate the frequency, course, risk factors, and neuroanatomy of hemispatial neglect in a large stroke cohort. Methods: One thousand two hundred eighty one patients with acute stroke were enrolled in a multicenter trial of an anticoagulant. Presence and severity of neglect were assessed with the NIH Stroke Scale (NIHSS) neglect item, assessing tactile extinction and visuospatial neglect at entry, daily for 1 week, and at 3 months. Head CT scans were obtained on day 7, and infarct location and size were characterized. Results: Neglect was common at presentation, occurring in 43% of right brain lesioned (RBL) patients and 20% of left brain lesioned (LBL) patients (p < 0.001). At 3 months, neglect was present in 17% of RBL patients and in 5% of LBL patients (p < 0.001). In RBL patients, neglect was most frequently associated with lesions involving the (in descending order) temporal, parietal, frontal, occipital lobes, basal ganglia, and thalamus. Neglect was more common and persistent with cortical than with subcortical lesions. Increasing age was associated with increased risk of neglect in RBL patients, whereas gender and handedness did not significantly affect neglect frequency. Conclusions: This series confirms that hemispatial neglect may occur with damage to several supratentorial structures but is most common and persistent with lesions of the right temporoparietal cortex. Increasing age is associated with neglect, parti cularly after right brain lesions. Gender and handedness do not exert a marked effect on the likelihood of the occurrence of neglect. Objective: To delineate the frequency, course, risk factors, and neuroanatomy of hemispatial neglect in a large stroke cohort. Methods: One thousand two hundred eighty one patients with acute stroke were enrolled in a multicenter trial of an anticoagulant. Presence and severity of neglect were assessed with the NIH Stroke Scale (NIHSS) neglect item, assessing tactile extinction and visuospatial neglect at entry, daily for 1 week, and at 3 months. Head CT scans were obtained on day 7, and infarct location and size were characterized. : Neglect was common at presentation, occurring in 43% of right brain lesioned (RBL) patients and 20% of left brain lesioned (LBL) patients (p <0.001). At 3 months, in RBL patients, neglect was most frequently associated with lesions involving the (in descending order) temporal, parietal, frontal, occipital lobes, basal ganglia, and thalamus. Neglect was more common an Increasing age was associated with increased risk of neglect in RBL patients, while gender and handedness did not significantly affect neglect frequency. Conclusions: This series confirms that hemispatial neglect may occur with damage to several supratentorial structures but is most common and persistent with lesions of the right temporoparietal cortex. Increasing age is associated with neglect, parti cularly after right brain lesions. Gender and handedness do not exert a marked effect on the likelihood of the occurrence of neglect.