It is generally accepted that inflammation of the walls of the heart, the small excursion of the auricular muscle, auricular fibrillation, and stasis are the major factors in the production of auricular thrombosis associated with mitral stenosis. Many investigators have reported the incidence of intracardiac thrombosis in rheumatic heart disease.1Jordan and co-workers,2reviewing 32 cases of mitral stenosis with systemic arterial emboli studied post mortem, found that the number of cases of left auricular appendage thrombosis alone (13 cases) was equaled by the number of cases in which clots occurred in the left atrial chamber alone (5 cases) plus the number of cases in which clots were found in the atrium and appendage simultaneously (8 cases). Daley and his co-workers 3 reported that thrombi were found as frequently in the left auricle as in the appendage in 39 cases of rheumatic heart disease studied post mortem. On