Radionuclide angiography and thallium-201 myocardial perfusion scintigraphy were compared in 31 patients with coronary artery disease studied at rest and during exercise. Seventeen of the 31 patients had perfusion defects on thallium-201 redistribution scans (61%); 16 of these had prior transmural infarction. Six other patients with prior inferior infarction had no defects on thallium-201 redistribution scans. During treadmill exercise, 28 of 31 patients (90%) developed new or larger thallium-201 perfusion defects, a significantly higher percentage of patients than those that developed ST segment abnormalities during exercise (74%). During bicycle exercise left ventricular ejection fraction decreased in 27 of the 31 patients (87%); the average change in left ventricular ejection fraction was from 54 +/- 16+ to 48 +/- 14% (p less than 0.1). Twenty-three of the 31 patients had abnormalities of regional ejection fraction at rest (74%), while 30 of the 31 had abnormalities during exercise (97%). The number of patients who developed new regional ejection fraction abnormalities during exercise (28 of 31) was not significantly different from the number of patients who developed new or larger thallium-201 myocardial perfusion defects during exercise. In order to compare the two radionuclide techniques with respect to identification of vessel involvement, the patients were separated into those with disease of the right coronary system, disease of the left coronary system, or both. Thallium-201 scintigraphy correctly identified ten of 14 patients with involvement of only the right or left system; radionuclide angiography correctly identified six of 14. However, radionuclide angiography identified more patients with right and left system involvement (15/17) than did thallium-201 scintigraphy (6/17), p less than .01. These data suggest radionuclide angiography is more useful for identifying patients with disease of both the right and left coronary arteries.