Seeking radical removal of chronic subdural hematoma using a simple and less invasive procedure, the author has devised a new method--replacement of the hematoma with oxygen via percutaneous subdural tapping. In this study, 40 patients were treated with this procedure. All patients made a full recovery after the treatment, without complications related to replacement of the hematoma with oxygen. Follow-up investigation showed recurrence of the lesion in two patients (5%). Because of its simplicity, reduced invasiveness, and short hospitalization, the procedure presented here is acceptable as an optimal therapeutic modality for chronic subdural hematoma in adults. Theoretical considerations supporting the safety of this procedure are discussed.