Thirty seven adult patients which chronic subdural haematoma were randomized into two groups. Eighteen patients served as controls and underwent evacuation of the haematoma via burr holes and a gravity dependent closed-system drainage. Nineteen patients comprised the study group. These patients had a continuous irrigation-drainage system installed in an attempt to facilitate the removal of fibrinolytic substances present in the haematoma fluid and to try to reduce the rate of rebleeding from the haematoma membranes. No differences were found between the pre- and post-operative clinical status, haematoma volumes and the degree of CT changes between the two groups. The complication rate was similar in the two groups. One patient in the study group and three patients in the control group required an extended period of drainage (24-48 hours) prior to the removal of the drains. All patients improved following the procedures. Within 30 days post the initial evacuation of the chronic subdural haematoma, re-operation was required in only one patient in the study group as opposed to four of the controls. This difference was not however statistically significant. When the need for re-operation was combined with the need for extended drainage period, a significant difference was shown in favour of the study group. These results indicate that drainage combined with continuous irrigation of the subdural space does not affect the clinical outcome of the patients, but significantly reduces the frequency of inadequate drainage of the haematoma and prevents longer drainage periods and repeated operations.