A survey of 89 patients with subdural empyema was conducted to assess the incidence of late seizures and morbidity in this disease. Twenty-four patients died during the acute stage of the illness and, of the 65 survivors, 13 were lost or had incomplete follow-up review. Hemiparesis occurred in 48 of the survivors during the acute stage, and all but nine recovered completely. Thirteen patients had a visual field deficit and all recovered; in three of these 13 who had speech disorders the deficits persisted. Recovery from neurological morbidity was not related to the type of surgical treatment; however, the mortality rate was improved by craniotomy. The same incidence of early seizures occurred in those who died (62%) as in those who survived (63%). Of those who had no early seizures, 42% had late seizures, the majority appearing within 16 months. Of those who had early seizures, 71% did not have subsequent attacks. The highest incidence of seizures occurred in patients who had their empyema in the second and third decades of life. The incidence of late seizures was not influenced by the method of surgical treatment, the degree of deterioration of consciousness during the acute stage of the illness, nor by occurrence of early seizures. A significantly increased incidence of early seizures was associated with paranasal sepsis, but not with late seizures.