Although the treatment of chronic subdural haematoma by burr hole drainage has been performed in the past with or without using a closed drainage system, the problem of intracranial air entrapment still persists and can cause a deterioration in the level of consciousness or seizures in the postoperative period. Cerebral infarction may also develop a few days after surgery because of the intracranial hypotension that occurs during the drainage procedure. In an attempt to minimise these complications and to prevent cerebral infarction and its attendant morbidity, we have developed a technique of treating chronic subdural haematoma--namely, performing burr hole drainage, irrigation and replacement of the haematoma with Hartmann's solution, and closed-system drainage of the subdural space with a silicone catheter. The blood pressure is closely monitored and maintained by the infusion of fluids throughout the procedure. An illustrative case using this technique is presented in this paper.