The author presents a discussion of research on cerebral arterial spasm. Arterial smooth muscle contraction, receptor, and relaxation mechanisms are presented in the context of what is known about cerebral arterial spasm and the biochemistry of vascular smooth muscle. Several new experimental approaches are suggested and a theoretical biochemical basis for the idea that damage to the artery alone could cause cerebral arterial spasm is postulated. Methods of determining cerebral arterial spasm and the need for a quantitative, in vivo method are discussed and the question of an irreversible stage of cerebral arterial spasm is considered. Finally, the problems associated with the delivery of a potentially successful treatment to the cerebral arterial smooth muscle cells are examined.