A review of the literature on the subject of the heart in myxedema reveals a certain amount of confusion concerning the true nature of the cardiac findings. There are those who feel that the findings are purely incidental; others believe that they are inherent in the disease. This lack of unanimity of opinion is found not only in clinical observations but also in experimental, physiologic and pathologic studies. In our attempt to throw light on this problem, it is our purpose to present a critical review of the literature and to report further clinical observations. REVIEW OF THE LITERATURE The first extensive study on the heart in myxedema was made by Zondek.1 His original contribution was based on four cases; later he mentioned additional cases. He found diffuse cardiac enlargement, occasionally limited to the left side, and by fluoroscopy he noted sluggish muscular contractions of the enlarged heart. In