A double femoral sound is described in patients with congestive heart failure of varied etiology. The factor common to all patients was a powerful atrial contraction secondary to increased right ventricular diastolic pressure or increased resistance to right ventricular filling. The first sound is produced by atrial systole transmitted by the venae cavae to the femoral veins; the second sound by left ventricular systole transmitted by the aorta to the femoral arteries. © 1960.