Ethyl alcohol produced graded contractile responses in rat cerebral arterioles and venules in vivo and in isolated canine basilar and middle cerebral arteries at a concentration range (10 to 500 milligrams per deciliter) which parallels that needed for its graded effects of euphoria, mental haziness, muscular incoordination, stupor, and coma in humans. Two specific calcium antagonists, nimodipine and verapamil, prevented or reversed the alcohol-induced cerebrovasospasm and thus may prove valuable in treating the hypertension and stroke observed in heavy users of alcohol.