Ten patients with intracranial lesions, anaesthetized with thiopentone and nitrous oxide (70%) in oxygen (30%) received etomidate 0.2 mg kg-1 i.v. Ventilation was controlled in each patient. Intracranial pressure (i.c.p.) and mean arterial pressure (m.a.p.) were recorded. I.c.p. decreased significantly in all patients (0.01 greater than P greater than 0.001). Although PaCO2 decreased during the period of measurement, the extent and time-course of this change suggested that it was not mainly responsible for changes in i.c.p. M.a.p. decreased in most patients, but the decrease was statistically significant only at 3 and 4 min after the administration of etomidate (0.05 greater than P greater than 0.02). The changes in cerebral perfusion pressure (c.p.p.) and heart rate were not clinically or statistically significant. We conclude that etomidate can be used for the induction of anaesthesia in patients with intracranial space-occupying lesions without increasing i.c.p. or seriously reducing c.p.p.