One hundred and thirty-three patients with chronic subdural hematoma were treated surgically between 1943 and 1980. The patients, aged 5 to 84 years, were graded retrospectively according to the Bender scale; 28% were in Grades 3 and 4. There were 107 unilateral and 26 bilateral hematomas. The clots were removed mostly via burr-holes without drainage. The treatment of 121 patients included an active policy of brain expansion at operation and the postoperative management of intracranial hypotension by lumbar injection. Two patients died, for a mortality rate of 1.5%. The patients who died were 54 and 59 years old, both from among the 26 cases with bilateral lesions; 107 unilateral lesions were treated, with no deaths. None of 51 patients who were aged 61 years and over died. The mean postoperative stay was 17.2 days, and at 3 weeks 77% had been discharged home. Fifteen percent of survivors had permanent disabilities. The common residual deficits were personality and memory disorders, and there was hemiparesis in Grade 4 cases. The high-risk groups of chronic subdural hematoma were those in Grades 3 and 4, bilateral hematomas, and the elderly. These seemed to be benefited by brain inflation and lumbar injections for intracranial hypotension.