Cerebral vasospasm following subarachnoid hemorrhage (SAH) is a common reaction induced by multiple factors with unclear mechanisms. This complication is difficult to treat and puts patient at risk for developing a delayed ischemic neurological deficit that can lead to substantial morbidity and mortality. Although numerous strategies have been suggested for the treatment and prevention of cerebral vasospasm following SAH, no definitive effect has been concluded in this regard. In this paper, we hypothesize that phosphodiesterase-5 inhibitors, tadalafil, can be used together with nimodipine, a calcium channel blocker, to prevent vasospasm in patients with subarachnoid hemorrhage. With synergic effects, the proposed drugs can promote relaxation of smooth muscles in spastic vessels. Keywords: Cerebral vasospasm; nimodipine; phosphodiesterase-5 inhibitor; subarachnoid hemorrhage; tadalafil