Magnetic resonance images of the leg were made preoperatively to show the vascular anatomy in twenty-nine patients (thirty-five legs) who were between the ages of fourteen and forty-one years and in whom we planned to use the fibula as a vascular graft. The fibula was harvested as a graft in thirty-two legs, and this allowed us to compare the images with the anatomical findings at operation. In these thirty-two legs, the branching pattern, the measured distance to the bifurcation of the peroneal artery, and all vascular anomalies in the area were accurately detected. No graft was taken from the other three legs. We recommend that imaging of the vascular anatomy of the leg be done before using the fibula as a vascular graft in order to detect the precise point of origin of the peroneal artery from the posterior tibial artery, to estimate the length of the vascular pedicle, and to evaluate the role of the three major vessels in supplying blood to the leg. All these aims can be accomplished with the aid of angiography, but we have found that gradient-recalled acquisition in the steady state (GRASS) magnetic-resonance imaging is more cost-effective and is associated with less morbidity. It is not adequate for older patients who have arterial stenosis or atherosclerosis or for patients who have some other underlying vascular disease. Metallic hardware may cause artefacts that obscure the vascular anatomy.