Sixty eight cases of chronic subdural hematoma (CSDH) surgically treated (December 1984-December 1988) with twist drill craniostomy (3-4 mm) and application of a closed drainage system (CDS) are reviewed. The patients were distributed in four groups depending on the density of the hematoma: hypodense (36 cases), isodense (6 cases), of mixed density (22 cases) and hyperdense (4 cases). In about one third of patients (25 cases) the duration of symptoms was shorter than one week, in 21 cases it was between one week and one month, and in 22 patients it was longer than one month. 77.95% of cases had a preceding head injury. Headache and motor deficits were the leading symptoms, being present in 43 (63.2%) and 42 (61.7%) cases, respectively. Twelve patients (17.6%) were comatose on admission. Twelve patients required reoperation. Six patients died (8.8%). The preoperative neurological status and associated systemic diseases influenced the outcome. We think that limited craniostomy with CDS is the therapy of choice for symptomatic CSDH.