Since December 1985, we have operated upon seven bicycle racers for endofibrosis of the external iliac artery. In all instances, the athletes had started cycling early in life and were engaged in top level competition by the age of 17. The principal complaint was intermittent claudication of one lower limb at "near-maximal" exercise. Pain could be reproduced by exertional tests on an ergometric bicycle, and in all cases except one, measurement of ankle systolic pressure of that limb compared with the opposite side and brachial pressures showed a marked decrease on the involved side. Arteriography, performed with multiple views and positions, documented a 5 to 6 cm moderately stenotic (less than 40% diameter) segment, associated with arterial lengthening. Surgical treatment consisted of endarterectomy and shortening of the artery. Four patients were able to return to competition. The origin of this pathology is discussed, based on gross and histologic findings. Under certain predisposing anatomic conditions, abnormal hemodynamics, probably due to a high flow arterial state and an aerodynamic position on the bicycle, provoke repeated trauma which eventually produces the lesion. Practically unrecognized until now with only two previous publications on the subject in the literature, this entity is probably not uncommon.