Fractional flow reserve (FFR) is an index of the physiological significance of a coronary stenosis and is defined as the ratio of maximal blood flow in a stenotic artery to normal maximal flow. It can be easily measured during coronary angiography by calculating the ratio of distal coronary pressure to the aortic pressure. FFR in a normal coronary artery equals 1.0. An FFR value of ≤0.80 indicates ischemia with an accuracy of more than 90%. The information provided by FFR is similar to that obtained with myocardial perfusion studies, but it is more specific and has a better spatial resolution, because every artery or segment is analyzed separately. This review outlines the utility of FFR in a number of conditions including multivessel disease, left main coronary artery stenosis, bifurcation lesions, myocardial bridging and myocardial viability. Furthermore, this review discusses the correlations between FFR with intravascular ultrasound and the economic considerations of the procedure in patients with coronary artery disease. © 2012 Future Medicine Ltd.