BACKGROUND Some stable angina patients with significant coronary function have low exercise capacity, whereas some have high exercise capacity. The aim of the present study was to determine whether coronary pressure-derived fractional flow reserve (FFRmyo), a functional index of coronary stenosis, is a better indicator of exercise capacity than angiographic stenosis. METHODS AND RESULTS The 15 male (65.8 +/-8.9 years old) subjects with stable angina and 75% angiographic stenosis underwent a cardiopulmonary exercise test (CPX), and peak oxygen uptake (PeakVO(2)) and oxygen uptake at anaerobic threshold (AT) were measured. The relationship between FFRmyo and CPX values was assessed. The left anterior descending artery was affected in 8 patients, the left circumflex artery in 5, and the right coronary artery in 2. Percent diameter stenosis (%DS) was 61.7 +/-9.1% by quantitative coronary angiography. Mean FFRmyo, PeakVO(2), and AT was 0.84 +/-0.66, 17.1 +/-3.2 ml x kg(-1) x min(-1), and 11.1 +/-2.0 ml x kg(-1) x min(-1), respectively. There was no significant correlation between %DS and FFRmyo, PeakVO(2), or AT (r=0.12, 0.051, and 0.013, respectively; P=NS), but FFRmyo had a significant positive correlation with PeakVO(2) and AT (r=0.534 and 0.542, respectively; P<0.05). CONCLUSIONS Exercise capacity reflects functional stenosis in stable angina patients.