The effects of benazepril hydrochloride (CGS 14824 A, CAS 86541-74-4), a novel angiotension I converting enzyme inhibitor, on the central nervous systems, were studied in experimental animals. Benazepril hydrochloride (3 or 10 mg/kg/d, p.o. for 14 days) dose-dependently inhibited the increase in the blood pressure caused by continuous norepinephrine (NE) infusion in spontaneously hypertensive rats (SHR) and suppressed in seizures induced by a monoamine oxidase inhibitor, tranylcypromine in NE infused SHR. Benazepril hydrochloride transiently increased spontaneous motor activity in mice, tended to inhibit acetic acid-induced writhing in mice and decreased fast wave sleep and slow wave deep sleep on EEG in cats at a high dose of 100 mg/kg p.o. However, benazepril hydrochloride at the same dose showed no effect on other central nervous and sensory systems in experimental animals.