A 68-YEAR-OLD WOMAN was admitted to the authors’ institution complaining of shortness of breath and chest pain. Her workup demonstrated a large (5 cm×5 cm) atrial mass by transthoracic echocardiography. She subsequently was scheduled for resection. On the day of surgery, transesophageal echocardiography confirmed the presence of this large, pedunculated left atrial mass, which originated from the interatrial septum just proximal to the orifice of the right superior pulmonary vein. Its visual appearance resembled that of a myxoma.