The right ventricular (RV) response to exercise was assessed in 32 patients with angiographically documented coronary artery disease and in 14 normal controls without cardiopulmonary disease. The relationships between exercise RV reserve, exercise left ventricular (LV) reserve, and the presence of proximal right coronary stenosis were also evaluated. RV and LV ejection fractions were determined using first-pass radionuclide angiocardiograms. The normal response to exercise was at least a 5% absolute increase in RV and LV ejection fractions. In the group with coronary artery disease, RV ejection fraction either decreased or remained the same with exercise (abnormal exercise RV reserve) in 19 of 32 patients. LV exercise reserve was abnormal in 26 of 32 patients. All 19 patients with abnormal exercise RV reserve had abnormal exercise LV reserve, and all six patients with normal LV reserve had normal RV reserve. There was a significant linear relationship between the direction and magnitude of change from rest to exercise of LV ejection fraction and RV ejection fraction (r = 0.77). In contrast, the RV response to exercise was not primarily dependent upon the presence or absence of proximal right coronary stenosis. These data suggest that abnormal exercise RV reserve occurs frequently in coronary artery disease and that the concomitant LV response to exercise appears to be its major determinant.