The concept of "cortical spreading depression" following subarachnoid hemorrhage (SAH) drastically tends to change the direction of vasospasm research. It has been rather confuse whether classical idea, delayed long-lasting major cerebral arterial contraction is real cerebral vasospasm or it occurs just after SAH and classical arterial contraction is an epiphenomenon. However, it is true that such sustained arterial contraction occurs following SAH, and the mechanisms still remain unclear. Intracellular signal transduction plays a pivotal role in long-lasting arterial contraction. Although scientific research advances, each role of signal transduction system has been getting clarified; overview or interrelations among such systems have to be more investigated. Based on the previous results, some aspect or part of streams of interrelation of signal transduction systems can be getting clearer. Such way to clarify the overview is extremely important to understand the real mechanisms of long-lasting arterial contraction following SAH ("classical cerebral vasospasm").