Published accounts of attempts at prevention or treatment of intracranial arterial spasm have been reviewed. These data are summarized in a table according to the agent tested, the dosage used, the route of administration, and the animal species used. Precautions are given concerning the organization and assessment of such studies. The best current management of patients with cerebral vasospasm involves promoting cerebral perfusion and avoiding detrimental factors. It may be possible in the future to identify those patients at risk of developing cerebral vasospasm, perhaps by assessing the location and amount of subarachnoid blood by computerized tomography. This would aid the development of measures to prevent intracranial arterial spasm, which seems to be a more promising approach to the problem than is treatment.