A 4-year retrospective study was made of 111 consecutive surgically treated patients with chronic or subacute subdural hematomas. All underwent single burr hole evacuation with accompanying saline irrigation of the subdural space. Postoperative outcomes at 6 weeks were 90% excellent, 5.5% fair, and 4.5% poor. Postoperative re-evacuation was performed either by needle aspiration or reoperation via the burr hole on 12 patients; one required a craniectomy and neomembrane stripping. These results compare favorably with previous data and support the use of the single burr hole technique as a simple and effective treatment of subacute and chronic subdural hematomas. This addresses the decompression of the brain parenchyma, the removal of the residual semisolid subdural hematoma component, and the removal, dilution, and inactivation of endogenous fibrinolytic agents.