Objectives. This study sought to determine the safety of deferral of percutaneous transluminal coronary angioplasty (PTCA) of angiographically intermediate but functionally nonsignificant stenosis, as assessed by coronary pressure measurement and myocardial fractional flow reserve (FFR(myo)). Background. Decision making in patients with chest pain and intermediate coronary stenosis remains difficult. In these cases it is unclear whether the risk of an intervention and the potentially subsequent restenosis outweigh the future risk of an event if the lesion remains untreated. FFR(myo) is a lesion-specific functional index of epicardial stenosis severity that accurately distinguishes stenoses associated with inducible ischemia. Methods. Retrospective analysis and follow-up was performed in 100 consecutive patients referred to our centers for PTCA of an intermediate stenosis but in whom the planned intervention was deferred on the basis of an FFR(myo) ≤0.75. Results. During a follow-up period of 18 ± 13 months (mean ± SD, range 3 to 42), two patients died of noncardiac causes. Ninety patients remained free of any coronary events, and their average Canadian Cardiovascular Society class decreased from 2.0 ± 1.2 at baseline to 0.7 ± 0.9 at follow-up (p < 0.0001). A coronary event occurred in eight patients and was target-vessel related in four. Conclusions. In patients with chest pain referred for PTCA of an intermediate stenosis, deferral of the intervention on the basis of an FFR(myo) ≤0.75 is safe and is associated with a much lower clinical event rate than if the procedure had been performed as initially planned in these patients.