The relationship of age to clinical and pathological findings was analyzed in 109 adult patients operated on because of chronic subdural hematoma. A well-formed membrane on the inner and outer surface of the hematoma was used as the criterion for chronicity of the hematoma. Younger patients had more evidence of increased intracranial pressure; older patients had more evidence of mental deterioration and pyramidal tract lesions. The interval from trauma to operation was shorter in the young patients. The thickness of the hematoma as measured from angiograms increased with the age of the patient. The cause of this difference is discussed.