In 8 patients having primarily an increased ICP, the effects of etomidate on ICP, arterial pressure and cerebral perfusion pressure (CPP) were studied by comparison with thiopentone. The patients received no premedication or basic anaesthesia and relaxation was obtained using pancuronium bromide. Blood gas analysis was performed at regular intervals to maintain a constant level of the arterial pCO2. Under the conditions of a reduced intracranial compliance and an elevated ICP, thiopentone lowered the arterial pressure considerably in contrast to etomidate. The primarily elevated ICP was reduced by both, etomidate and thiopentone to an extent of 27 per cent for more than 10 min. The considerable decrease of arterial pressure by thiopentone caused marked lowering of CPP during more than 10 min. In the same period etomidate did not influence either arterial pressure or CPP. These results show that for the induction of anaesthesia in neurosurgical patients having a primarily increased ICP etomidate has good properties.