Intracranial pressure was measured under the influence of the new hypnotic etomidate (Dosage: 0.15 to 0.30 mg/kg b.w.). For comparison thiopentone (Trapanal: 3 to 4.5 mg/kg) and methohexitone (Brevimytal: 1 to 1.5 mg/kg) were given. The investigations were performed on 28 neurosurgical patients, who thereafter underwent surgery. The patients already had a closed or open ventricular catheter by means of which intracranial pressure was continuously measured. Etomidate lowered intracranial pressure. This happened during induction of anaesthesia and later during neuroleptanalgesia when etomidate was again injected. The pressure fall after etomidate was similar to that seen after thiopentone. It was at the time of induction 5 and later on 3mm Hg. Methohexitone showed a somewhat smaller effect. The cerebral perfusion pressure was calculated. When etomidate was given during the course of a neuroleptanalgesia the cerebral perfusion pressure merely decreased slightly (-7 per cent). Perfusion pressure remained stable after thiopentone and methohexitone.