A simple method of bedside twist-drill craniostomy and closed-system drainage for evacuation of chronic and subactue subdural hematoma is introduced. The principles and theoretical considerations that form the basis for this technique are discussed. The technique was used in 21 patients with chronic or subacute subdural hematoma; it has produced results superior to those of the conventional methods used in our patient population. Possible mechanism responsible for the better results with the simple twist-drill closed-system drainage are described.