In 311 patients (269 men and 42 woman, 20 to 65 years old) without transmural myocardial infarction the results of exercise tests in supine position were compared with the results of coronary angiography. 1. Patients having ischemic ST-segment depression (greater than or equal to 0.1 mV) and angina pectoris during exercise (n = 108) showed a greater than or equal to 50% stenosis of at least one vessel in 86.1%. In men the number of a greater than or equal to 50% stenosis was significantly higher than in women (91.3 vs. 56.2%). In patients without digitalis agreement with coronary angiographic findings is higher than in patients with digitalis (92.7 vs. 79.2%). After excluding women, patients under digitalis and those with an intramural myocardial infarction, agreement was 96.8%. 2. In patients having ischemic ST-segment depression agreement was 30% and in those with angina pectoris 36.8%. 3. In patients having neither ischemic ST-segment depression nor angina pectoris during exercise up to a heart rate of 80% of the age-dependent heart rate limit a coronary angiogram without a greater than or equal to 50% stenosis was found in 87.6%. After excluding patients with an intramural myocardial infarction, women and patients under digitalis, agreement increased to 97.9%. 4. In patients having both ischemic ST-segment depression and angina pectoris during exercise a 2- or 3-vessel disease was more often found than in patients having either ischemic ST-segment depression or angina pectoris, or in those having neither ischemic ST-segment depression nor angina pectoris respectively (57.5% vs. 16.6, 8.9 and 1.9%). 5. The number of positive coronary angiograms, especially of 2- and 3-vessel disease, increases with the degree of an ischemic ST-segment depression and the reduction of exercise tolerance.