40 patients with acute inferior myocardial infarction (MI) associated with persistent precordial ST segment depression greater than or equal to 0.1 mV underwent coronary arteriography and left ventriculography within 5-6 days of their admission. The inferior MI was the result of complete occlusion of the right coronary artery (RCA) in 38 patients and the result of complete occlusion of the posterior descending artery (PDA) coming off the circumflex artery (Cx) in two patients. 36 (90%) of the 40 patients showed one or more severe stenoses in the left anterior descending artery (LAD). 12 of the 36 patients had severe triple vessel disease. The 36 patients whose coronary arteriograms showed significant LAD stenosis had an emergency coronary artery by pass graft (CABG) operation. Soon afterwards the precordial leads were normal and the patients free of angina till their discharge from hospital. We conclude that a persistent precordial ST segment greater than or equal to 0.1 mV depression in acute inferior MI is highly predictive of significant LAD disease.