A consecutive series of 48 adult patients with a chronic subdural hematoma is reported. These patients were treated according to a protocol consisting of a sequence of conventional surgical procedures ranging from simple burr-hole drainage to craniotomy and subdural membranectomy. Seven patients (15%) continued to demonstrate severe neurological dysfunction, or suffered acute neurological deterioration after completion of this protocol. However, after undergoing excision of the cranial vault overlying the hematoma site, six of these seven patients demonstrated a significant clinical improvement. Based on analysis of these seven cases, the authors suggest that craniectomy be considered in those patients who suffer a symptomatic reaccumulation of subdural fluid following craniotomy and membranectomy, or who demonstrate further neurological deterioration as a result of cerebral swelling subjacent to the hematoma site. However, this procedure probably has no efficacy once extensive cerebral infarction has occurred.