SUMMARY In a series of 750 coronary cinearteriograms, coronary spasm was observed in only seven individuals. At the time of the cinearteriogram, three experienced an attack of chest pain that had all the features of coronary insufficiency before the spasm was relieved by nitroglycerin. One of these three patients displayed an acute myocardial injury pattern on the electrocardiogram, another one went into cardiac standstill which responded to external massage. Coronary spasm is probably due to the action of catecholamine on the alpha receptors of the large coronary vessels, whereas myocardial anoxia can still be considered the immediate cause of the cardiac pain. Differences in the symptomatic manifestations occurring during coronary spasm may be due to the degree of arterial narrowing, to the presence or absence of coronary artery disease and also to individual differences in pain threshold. TABLE 2ASHDCaseSexAgeVessel InvolvedCatheter InducedChest PainSpasmRCAAnt. Desc.Circ.LV D2 mm Hg1M53RCA--†---102M37LCA*-†---73M55Ant. D.**†---64M43RCA-*‡---105M47RCA--†*‡†106M49RCAX-†-‡*157M32RCA-*‡---11Abbreviations: RCA=Right coronary artery; LCA=Left coronary artery; Ant. Desc.=Anterior descending branch of left coronary artery; Circ.=Circumflex branch of left coronary artery; ASHD=Arteriosclerotic heart disease; LV D2=Left ventricular end diastolic pressure. Severity of ASHD or of coronary spasm:*=Mild luminal narrowing, less than 20 per cent caliber reduction†=Moderate narrowing, more than 20 and less than 75 per cent caliber reduction‡=Marked narrowing, over 75 per cent caliber reduction. Whatever its final mechanism, coronary spasm may, in an occasional individual, be responsible for an attack of angina pectoris and even for sudden death.