Serial cerebral blood flow (CBF) measurements were made with stable xenon-enhanced computed tomography in 20 patients with angiographically confirmed ruptured intracranial aneurysms, before and during induced hypertension with continuous infusion of dopamine. All patients showed angiographic vasospasm during their course. Twelve patients without symptomatic vasospasm (Group 1) had the lowest hemispheric CBF on the craniotomy side of 31.6 ± 6.8 ml/100 gm/min on days 4-9 (control value, 40.1 ± 2.0 ml/100 gm/min), while the other eight patients with symptomatic vasospasm (Group 2) had the lowest hemispheric CBF on the craniotomy side of 25.0 ± 7.6 ml/100 gm⁄min on days 10-14. The critical hemispheric CBF inducing neurological deficits was about 20 ml/ 100 gm/min in Group 2. Dysautoregulation was usually present in Groups 1 and 2, but therapeutically induced hypertension could reverse the delayed neurological deficits, if begun early at the stage of delayed vasospasm.