The findings at coronary arteriography and ventricular angiography in 52 patients with a restricted myocardial infarct were compared with those of 106 patients with acute coronary insufficiency and 100 with transmural infarcts. Certain features place restricted myocardial infarction in an intermediate category when compared with the two other syndromes. The percentage of coronary occlusions was significantly higher in transmural infarction (23.5%) and in restricted infarction (16.6%) than in acute coronary insufficiency 6.8%). Study of the vessel beyond a tight stenosis (greater than or equal to 75% was particularly effective in clearly separating the three groups. As a result, 63% of patients with coronary insufficiency, 40% of these with restricted infarcts, and only 23% of patients with a transmural infarct could be referred for surgery. Ventricular angiography showed a close relationship between restricted infarction and acute coronary insufficiency because ventricular function appeared normal or subnormal (localised hypokinesia) in 69% and 81% of cases respectively, compared with 4% of cases of transmural infarction. Restricted myocardial infarction appears to resemble coronary insufficiency, but shows elevation of enzymes and often more marked disease of distal vessels.