Affiliated Hospital. Second Military Medical College. ShanghaiForty-two cases of chronic subdural hematoma were treated by irrigation and drainage. Symptoms of elevated intracranial -pressure, localizing neurologic signs and cerebral angiography established the diagnosis. Operative treatment consisted of evacuation of the hematoma by repeated irrigation through burr holes made on the frontal and parietal side of the hematoma. A plastic tube was placed through the parietal hole for continuous drainage for three to four days. The above mentioned treatment is simple to perform and rather safe even for the senile and debilitated patients. Among 44 patients all 19 preoperatively unconscious patients regained consciousness postoperatively. Twenty-three cases were followed up from one to seventeen years. All patients recovered completely without recurrence of hema-toma or epilepsy, except one patient who is still having hemiparesis at present.