Forty male patients with chronic stable angina pectoris and no prior myocardial infarction were studied by planar thallium scintigraphy with use of circumferential profile analysis. Ischemic defects were assessed by measuring degrees of circumference involved and area of defect. Data were collected for 3 vascular regions in each of 3 views (anterior, 45 degrees and 65 degrees left anterior oblique projection). Patients were then randomized to exercise and control groups, the former training for a period of 1 year using the Canadian Airforce plan for physical fitness. After 1 year, both groups were restudied. Exercise training produced a 34% reduction in degrees of ischemia overall (p less than 0.02), the most significant change being seen on the anterior view (72 degrees +/- 59 degrees before vs 30 degrees +/- 35 degrees after training). Regional analysis showed markedly improved perfusion anterolaterally and apically on the anterior view and anteroseptally on the 65 degrees left anterior oblique view. These improvements support the hypothesis that exercise training improves myocardial perfusion by enhanced collateral function.