OBJECTIVE To evaluate the techniques and efficacy of intracranial intraarterial papaverine infusion for symptomatic vasospasm after subarachnoid hemorrhage caused by aneurysm rupture. METHODS Papaverine was infused on 19 occasions in 14 patients, 6 hours to 2 days after spasm became apparent clinically. Sixty vascular territories were treated. Infusion was made into the supraclinoid internal carotid artery 20 times, cavernous internal carotid artery once, selective A1 anterior cerebral artery 8 times, M1 middle cerebral artery 7 times, and basilar artery 3 times. Papaverine doses ranged from 150 to 600 mg and exceeded 400 mg on 8 occasions. RESULTS Angiographic improvement occurred in 18 (95%) of the 19 treatment sessions: results were excellent in 3 sessions, moderate in 8, and mild in 7. The best angiographic results often were obtained with superselective infusion, although angiographic results did not always correlate with clinical response. Seven (50%) of the 14 treated patients showed dramatic acute clinical improvement within 24 hours of papaverine therapy, and there was no clinical evidence of recurrent vasospasm in these patients. Recurrence of angiographic vasoconstriction was demonstrated in three patients; one showed marked clinical improvement after a second treatment. There were no episodes of systemic hypotension in any of the cases. Monocular blindness developed in one patient because of papaverine infusion near the ophthalmic artery. CONCLUSIONS Papaverine was effective in dilating narrowed arteries in most patients with symptomatic vasospasm caused by subarachnoid hemorrhage. This series showed encouraging clinical results with no recurrence of neurologic deterioration in those patients who responded well to papaverine. Superselective infusion appears to be indicated in some cases for adequate papaverine delivery.