We reviewed 49 patients with Wernicke's aphasia resulting from a stroke. Their aphasia was classified on the basis of comprehensive neuropsychological testing. Wernicke's aphasia was more common in older patients and in men. Cerebral infarction occurred in 38 patients (78%) and intracerebral hemorrhage in seven (14%); the remaining four patients (8%) developed aphasia after surgery for aneurysmal subarachnoid hemorrhage. Embolic events were the most common etiology of Wernicke's aphasia in the 38 patients with cerebral infarction, with cardiac emboli in 40% and large-vessel atheroemboli from a carotid source in 16%. In patients with Wernicke's aphasia secondary to infarction, an embolic source should be sought. Patients with Wernicke's aphasia should have computed tomography to exclude intracerebral hemorrhage before institution of anticoagulant therapy.