Nineteen patients with traumatic subdural hygroma (TSH) who were admitted between 1988 and 1992, were reviewed. Diagnosis of TSH was made by serial computerized tomography (CT) after initial head injury, and patients were followed for up to 19 months after head injury. The patients ranged in age from 53 to 91 years (mean 75.6 yrs). Fifteen patients were treated conservatively, and 4 patients underwent surgery. Patients had disturbance of consciousness (transient in 5 cases, persisting in 3 cases), headache (10 cases), vomiting (6 cases), and vertigo (2 cases). TSH began to develop within 24 hs in 10 patients after initial head injury, and in 13 (68%) of 19 patients, TSH was demonstrated within 72 hs after the initial head injury. Chronic subdural hematoma (CSH) developed in 5 (26%) of 19 patients and 2 patients underwent surgery. In 15 patients, who were treated conservatively, TSH disappeared in 10 patients, and decreased in 4 patients, but remained unchanged in 1 patient. Clinically, 11 patients improved. Three patients remained unchanged. One patient, who had cerebral contusion, died of pneumonia. In 4 patients, who underwent surgery, including 2 patients with CSH, TSH disappeared in all patients. Two patients improved, and 1 patient was unchanged. Another patient, who had cerebral contusion and normal pressure hydrocephalus, died. In general, clinical outcome was satisfactory, except for the patients who had accompanying parenchymal lesions before or after head injury. Surgical treatment was limited to the patients who had rapidly enlarging TSH and neurological deterioration.