IT HAS LONG been known that peripheral pulses which are easily palpable at rest may disappear during claudication induced by exercise.1-3 This was formerly attributed to arterial spasm.3-6 Later it was realized that arterial pulsations at the ankle normally decrease during moderate exercise2,7,8 and that loss of the pulse in occlusive arterial disease is an exaggeration of this normal response. Experimental studies in which blood flow and pressure have been measured indicate that in the presence of an arterial stenosis or occlusion, vasodilation, induced by exercise or pharmacologic agents, is associated with increased blood flow and a fall in mean arterial and pulse pressure distal to the arterial lesion.9,10 Method Fourteen stenotic and one occlusive (case 3) arterial lesions were studied (Table). Ten of the lesions were associated with a resting distal pulse that was lost to palpation with exercise-induced claudication11 or papaverine injection. In two