Traditionally coronary artery spasm, which is implicated in the pathogenesis of angina, myocardial infarction and sudden death, has been perceived as involving either a powerful spasmogen or larger quantities of a less potent stimulant. The present essay proposes that spasm may occur in the complete absence of any inciting chemical or spasmogen. Sudden intense coronary artery constriction may reflect an abnormality in an intrinsic system of tone regulation involving pacemaker cell discharge, intercellular conduction through gap junctions to adjacent cells, and the cycling of extracellular and bound calcium. Defects in spontaneous tone generation and recovery, may be primary factors in the causation of clinically occurring coronary artery spasm and its sequela.