Chronic subdural haematoma (CSDH) is one of the most common clinical entities in daily neurosurgical practice. To evaluate the clinical features, computed tomography findings, surgical results, and complications our series was statistically analysed to elucidate the factors affecting the post-operative outcome. A retrospective study (1980-2002) of the records of 1000 patients harbouring 1097 chronic subdural haematoma treated with burr-hole craniotomy with closed-system drainage was carried out. The series included 628 males and 372 females, age range 12-100 years, mean age 72.7+/-11.4 years. The mean interval from trauma to appearance of clinical symptoms was 49.1+/-7.4 days (15-751). The principal symptom was headache (29.7%) in the over 70s, and behavioural disturbance (33.8%) in the under 70s. The CSDH was right sided in 432 patients, left sided in 471, and bilateral in the remaining 97 cases. Post-operative complications occurred in 196 patients and 21 patients died in hospital. Poor prognosis was related to patient's age (>70) and clinical grade on admission (grades 0-2 versus grades 3-4).