A moderate controlled hypotension has been performed with isoflurane in the presence of nimodipine (4 mg.h-1) on ten patients anesthetized for cerebral aneurysm clipping. The administration of both drugs induced a dose-dependent hypotension secondary to the reduction of the systemic vascular resistance without impairment of cardiac index. Nimodipine did not modify the cardiovascular effects of isoflurane. It is concluded that intravenous administration of nimodipine should be continued during the operative period.