We studied retrospectively 143 adult patients treated in our department from 1979 to 1991 for chronic subdural haematoma (SDH) in order to identify the incidence of seizures and the necessity for prophylactic anticonvulsant treatment. Furthermore, after review of the literature, we selected an additional 879 cases for comparison. Results indicated a low incidence of epilepsy. Before surgery 5.6% of patients in our series and 4.3% in the literature had epilepsy, whereas after surgery, the frequencies were 3% and 1.8%, respectively. According to our data, antiepileptic drugs need not be administered prophylactically in patients with chronic SDH. But the situation is different for alcoholic patients, because they have a major risk of epilepsy.