To assess the prognostic implications of the left ventricular (LV) ejection fraction (EF) responses to exercise, a measure of reversible myocardial ischemia in pts with coronary artery disease (CAD), we studied 138 CAD pts who had mild angina with radionuclide angiography. Rest or exercise LVEF did not identify the 8 pts who subsequently died or the 16 pts who required operation for increased angina during the mean 2 year follow-up period. However, the change in EF from rest to exercise was predictive: 7% of pts with positive change EF died or underwent operation compared to 24% of pts with negative change EF (p less than 0.05). Thus, the absolute level of LVEF at rest or exercise does not predict which pts would progress, but the change EF helps to define subgroups at low and at high risk.