This paper reports the effect of 12 mo of intense endurance exercise training on the plasma catecholamine response to exercise in 11 male patients [aged 50 +/- 8 yr (mean +/- SD)] with coronary artery disease. A substantial adaptation to training was attained as evidenced by a 42% increase in maximum O2 uptake capacity. At rest, heart rate was lower after training, but resting blood pressure and plasma catecholamines were unchanged. At the same absolute work rate, plasma norepinephrine and epinephrine levels, rate pressure product, and ischemic S-T segment depression were all significantly lower after training. A higher plasma norepinephrine level was attained at maximal exercise after training (2,049 +/- 654 before vs. 3,408 +/- 1,454 pg/ml after, P less than 0.025); this was associated with a higher systolic blood pressure (175 +/- 25 before vs. 188 +/- 22 mmHg after, P less than 0.025) and a higher rate-pressure product (25.3 X 10(3) +/- 4.5 X 10(3) before vs. 27.6 X 10(3) +/- 5.2 X 10(3) after, P less than 0.025). Despite the higher plasma norepinephrine level and rate pressure product, S-T segment depression at maximal exercise was unchanged. These findings suggest that some patients with coronary arterial disease can attain a higher myocardial O2 requirement, without electrocardiographic evidence of increased ischemia, after prolonged strenuous exercise training.