Fifty-eight of 220 consecutive patients had exercise-induced ST depression in some or all precordial leads 3 to 12 months after a first inferior myocardial infarction. All 58 patients underwent thallium-201 exercise testing, 2-dimensional echocardiography and coronary angiography. ST depression was confined to leads V1-4 in 22 patients (group A); thallium-201 exercise testing showed reversible anterior perfusion defects and left anterior descending coronary artery disease in 11 of the 22 patients (50%). None of the other 11 with negative thallium-201 exercise test results had significant left anterior descending narrowing, and the anterior ST depression could be explained by asynergy of the posterior wall found on 2-dimensional echocardiography in 10. ST depression appeared in leads V5-6 in 22 patients (group B); reversible anterior perfusion defects and left anterior descending disease was demonstrated in 18 patients (82%). In the other 4 patients posterior wall asynergy was demonstrated. ST depression was seen from leads V1-6 in 14 patients (group C); reversible anterior perfusion defects were seen in 6 patients (43%), 5 of whom had significant left anterior descending disease. Among the other 8 patients without reversible anterior perfusion defects, posterior wall asynergy was found in 6.(ABSTRACT TRUNCATED AT 250 WORDS)