The use of physostigmine electively to reverse the effects of droperidal and diazepam has permitted an optimum level of neuroleptanaesthesia in neurosurgical operations where co-operation of the patient is required during part of the procedure. The patient can be put to sleep or readily awakened to be fully co-operative depending on the needs of the surgeon. In this series of seven anaesthetics there were no side effects from the small doses of physostigmine employed. Bradycardia and salivation were not a problem. One child vomited once. Atropine was not necessary. Since a narcotic antagonist is not needed, a reasonable degree of analgesia can be maintained in these patients while they are awake. The latent time for the effect of physostigmine was two to four minutes and the effect of an intravenous dose lasted from 35 to 45 minutes. With physostigmine, these patients wake up gently as though from normal sleep. If neurological assessment is required post-operatively, drowsiness due to drugs can be reversed by giving more physostigmine and the level of consciousness can then be assessed.