AbstractFour patients with left atrial myxoma were studied using high speed B mode echocardiography with a mechanical sector scanning system. In all four patients, a mass of echoes was recognized in the left atrial chamber during systole. Its lower portion protruded into the left ventricle through the mitral orifice in diastole. The degree of protrusion of the tumor echo varied. An analysis of three cross sections, long axis of left ventricle, sagittal and horizontal axes, showed that the tumor moved anterosuperiorly to posteroinferiorly in the left‐sided heart chambers. Its movement was clearly observed in real time. The echo pattern from the tumor had an appearance of mottling, not layering. The myxomas were successfully removed from the left atrial chambers by surgical intervention in all case