The clinical findings and computerized tomography (CT) brain scans of 45 patients with supratentorial intracerebral hematomas were evaluated to determine the effect of hematoma location on the clinical course and outcome of the disease. The lesions were frontal in 18 patients, temporal or temporoparietal in 17, and parieto-occipital in 10. No patient with a frontal or parieto-occipital hematoma had clinical signs of transtentorial herniation at admission or subsequently, whereas seven (41%) of those with temporal or temporoparietal lesions had signs of herniation (p less than 0.05); three of these seven patients had an abnormal mental status, ipsilateral anisocoria, and lateralizing motor findings at admission, and four developed these signs within 12 hours after admission, necessitating urgent surgical intervention. The mean volume of the lesions estimated from the CT scans was similar in the three groups (frontal 47 +/- 28 cc; parieto-occipital 53 +/- 26 cc; temporal/temporoparietal 41 +/- 21 cc). None of the six patients with temporal or temporoparietal hematomas smaller than 30 cc had signs of tentorial herniation, compared with seven (64%) of 11 patients with larger hematomas (p less than 0.05); in six of these seven cases, the hematoma was caused by head injury. Patients with a temporal or temporoparietal hematoma had a worse outcome than those in the other two groups, and no patient with signs of tentorial herniation had a good outcome. Patients with temporal or temporoparietal hematomas appear to be at greater risk of brain-stem compression, especially if the lesion is larger than 30 cc and caused by head injury, than are those with hematomas in other sites. In such cases, prompt surgical intervention should be considered.