AbstractFour unusual cases of phasic (occurring only in systole or only in diastole) coronary artery narrowing are reported. In two cases, diastolic compression of the left anterior descending coronary artery was due to tight pericardial adhesions in patients with aortic insufficiency; in the third case, systolic compression of two right ventricular coronary branches was associated with hypertrophic cardiomyopathy and a normotensive right ventricle; and in the fourth case, a large aneurysm of the inferior wall of the left ventricle caused systolic compression of the posterior descending coronary artery, which was epicardial. The diagnostic and pathophysiologic characteristics of each case are discussed.