The many important features of selective cine-coronary-arteriography to show the coronary arterial tree are demonstrated in the study of 130 such investigations carried out in patients with unstable angina. Cine-coronary-arteriography shows up the extent and location of obstructive atherosclerotic lesions. Ventriculography, together with measurement of ventricular pressures, gives information about the function and kinetic status of the left ventricle. These two investigations which do not, in our opinion, carry a greater risk in these cases than in cases with chronic angina, allow a precise diagnosis to be made. The early discovery of major lesions before infarction has occurred allow conclusions to be drawn about the prognosis and the appropriate treatment.