This study evaluated whether first-pass perfusion cardiovascular magnetic resonance (FP-CMR) could predict the hemodynamic significance of epicardial coronary artery stenosis as defined by invasively determined fractional flow reserve at coronary angiography. In 19 patients with known coronary artery disease (CAD), the hemodynamic relevance of 22 stenoses (mean angiographic severity 73 +/- 9%) was determined using fractional flow reserve measurements (cutoff 0.75). Results were compared with a territorial index of myocardial perfusion reserve (MPR) derived from FP-CMR. In addition, 9 age-matched patients with low prevalence of risk factors and without CAD at angiography served as a control group. A cutoff of 1.5 for MPR separated hemodynamically relevant from nonrelevant stenoses with a sensitivity and specificity of 92% and 92%, respectively. The area under the receiver-operator characteristic curve was 0.97. In the patient group, territories supplied by arteries without significant stenosis (<or=50%) showed a lower MPR compared with the control group (p <0.0001), suggesting the presence of microvascular dysfunction. In conclusion, FP-CMR may be useful for assessment of the hemodynamic relevance of angiographically undetermined CAD.