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The clinical symptoms of stroke may result from the infarction of brain tissue or from the occurrence of a hemorrhage within the brain itself. Prior to the development of modern imaging techniques, many brain hemorrhages were not recognized as such, and were diagnosed as infarctions based on the patient's symptoms. CT scanning and magnetic resonance imaging (MRI) now permit the clear distinction of infarction from primary hemorrhage. (Of course, some hemorrhage may also occur as a secondary consequence of infarction.) The Stroke Data Bank was organized as a large prospective study for the evaluation of stroke patients. Of the 1,805 patients in the data bank, 237 had parenchymous hemorrhage. (This is a hemorrhage within the brain substance itself, distinct from other cranial hemorrhages such as a subarachnoid hemorrhage resulting from an aneurysm.) Thirty-four of these hemorrhages were secondary, and 31 were in the brain stem or cerebellum. The remaining 172 may be divided into lobar hemorrhages, which lie within or just under the cerebral cortex, and deep hemorrhages, which affect the central gray matter. (The central gray matter, deep within the brain, includes the basal ganglia and the thalamus.) Severe headache was a more common symptom among the 65 patients with lobar hemorrhage. Motor deficits were more common among the 107 patients with deep hemorrhage. Hypertension, the most important risk factor for cerebral hemorrhage, was more common among the patients with deep hemorrhage. Many other clinical features, such as seizures, focal neurological deficits, and decreased consciousness or coma, were found with comparable frequency among the patients with lobar hemorrhage and those with deep hemorrhage. (Consumer Summary produced by Reliance Medical Information, Inc.)