Cerebral vasospasm secondary to aneurysmal subarachnoid hemorrhage that has become refractory to maximal medical management can be treated with selective intra-arterial papaverine infusions. Papaverine is a potent vasodilator of the proximal, intermediate, and distal cerebral arteries and can improve cerebral blood flow (CBF). When infused intra-arterially using endovascular microcatheter techniques, papaverine can effectively increase angiographic vessel diameter, decrease prolonged cerebral circulation time, and improve cerebral oxygenation. However, one of the major disadvantages of papaverine is its transient nature, which can result in recurrent and/or persistent angiographic and clinical vasospasm that may require multiple repeated infusions, despite a successful response to the initial treatment. Intra-arterial papaverine can be used alone or in combination with balloon angioplasty. This article reviews the mechanism of action, technique of administration, effects on CBF, clinical results, and complications of intra-arterial papaverine for the treatment of cerebral vasospasm.