Chronic hemorrhagic spasm of the basilar artery was produced in beagle dogs by introducing blood into the cisterna magna. Spasm was evaluated by means of vertebral angiography. Papaverine hydrochloride was administered intravenously, intracisternally as well as intra-arterially. The intracisternal route was the more effective in combating spasm but the effect was transitory. The results suggest that the treatment of spasm by chemical means in subarachnoid hemorrhage using agents currently available would require continuous topical application.