Significant differences in the hemodynamic response to upright and supine exercise have been reported in patients with coronary artery disease. The purpose of the present study was to compare the degree of myocardial ischemia as assessed by ST segment depression during upright treadmill and supine bicycle exercise in 98 patients with coronary artery disease and in 34 patients with normal coronary arteries. The amount of ST segment depression at maximal exercise in patients with coronary artery disease was 0.90 +/- 0.80 mm for treadmill and 1.34 +/- 1.09 mm for supine bicycle (p less than 0.001). The amount of ST segment depression during treadmill and supine bicycle exercise tests was also compared at highest similar heart rates (0.68 +/- 0.77 versus 1.17 +/- 1.01, p less than 0.001), at highest similar rate-pressure products (0.71 +/- 0.77 versus 1.08 +/- 1.04, p less than 0.001), at highest similar metabolic equivalents of oxygen consumption (MET) levels (0.69 +/- 0.75 versus 1.20 +/- 1.05 mm, p less than 0.001) and at the onset of angina (0.84 +/- 0.73 versus 1.18 +/- 0.88 mm, p less than 0.001). The rate-pressure product achieved at maximal exercise was similar in both tests (18.74 +/- 5.80 x 10(3) versus 18.81 +/- 5.17 x 10(3), p = NS). The occurrence of angina during treadmill and supine bicycle exercise tests was similar (47 of 98 versus 48 of 98, respectively, p = NS). For the detection of coronary artery disease, the sensitivity was 50.0% for treadmill and 63.3% for supine bicycle (p less than 0.05) and the specificity was 73.5 versus 70.6%, respectively (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)