To evaluate the significance of audible gallop sounds in the right supraclavicular fossa we performed simultaneous external heart sound recordings at 50 and 100 Hz at the left ventricular apex, left sternal border, and right supraclavicular fossa in 50 patients with audible gallop sounds at the left ventricular apex. In each patient heart sounds were recorded with a simultaneous jugular phlebogram, apex cardiogram, and carotid pulse tracing. In 44 patients an apical fourth heart sound coincident with the 'a' wave of the apex cardiogram was recorded, and in 32 (73%) the fourth heart sound was audible and recordable in the right supraclavicular fossa. A left ventricular third heart sound, coincident with the rapid filling wave of the apex tracing, was present in 25 patients but was recorded in the right supraclavicular fossa in only 7 (28%). Intracardiac phonocardiography (high-fidelity catheter) was performed in six patients with left ventricular gallop sounds and in each instance arterial transmission of the third or fourth heart sound, or both, was present. Five additional patients had a prominent jugular venous 'a' wave, but only two had a soft parasternal fourth heart sound. Intracardiac phonocardiography in these five patients failed to reveal transmission of right ventricular gallop sounds to the superior vena cava. We conclude that since left ventricular gallop sounds commonly are transmitted to the right supraclavicular fossa auscultation in this area is often helphful in their detection. In addition, a prominent jugular venous 'a' wave sometimes produces recordable presystolic vibrations that are occasionally audible as well.