Large subcortical infarctions may be due to cerebral embolism and cause cortical signs more frequently than small subcortical infarctions, which usually result from small-vessel disease and are not associated with cortical findings. We evaluated 51 consecutive patients with a subcortical infarct on CT that was 1.5 cm or larger for a potential carotid or cardiac source of embolism and determined how frequently aphasia, hemineglect, or gaze paresis occurred. A carotid or cardiac embolic source was identified in 63% of the total population with a carotid source occurring in 23% and a cardiac source occurring in 49%. More than one-half of the patients with hypertension or diabetes mellitus had an embolic source, whereas all patients without these risk factors had a possible carotid or cardiac source of embolism. Aphasia or hemineglect occurred in 39% of patients and gaze paresis occurred in 41%. Large subcortical strokes frequently result in a different clinical syndrome and from a different mechanism than small subcortical strokes.