This study was undertaken to determine whether adaptation to 12 months of intense endurance exercise training could alter the relationship between the product of heart rate and systolic blood pressure (double product) and the extent of ischemic ST-segment depression during exercise in patients with coronary artery disease. True (i.e., not symptom-limited) maximum oxygen uptake capacity increased from 25.5 ± 4.2 ml/kg/min (mean ± SD) to 35.3 ± 4.4 ml/kg/min with training. The maximum degree of ST-segment depression during exercise averaged 0.20 ± 0.04 mV before and 0.16 ± 0.08 mV after training despite a 20% increase in maximum double product. The double product at which ST depression (0.1 mV) first appeared was 22% greater after training. The extent of ST-segment displacement at the same double product was less after training. These findings suggest that training, if sufficiently intense and prolonged, can result in a reduction in myocardial ischemia at the same of a higher double product.