Transesophageal echocardiogram is the procedure of choice in the evaluation of masses located in the cardiac chambers. In this paper three cases of atrial thrombosis are presented: a) a free floating ball thrombus in the left atrium in a patient with moderate mitral stenosis; b) three thrombotic masses adherent to a central venous catheter; c) three thrombotic masses attached to Chiari s network in a patient operated for an ostium secundum atrial septal defect one year before. In all cases transesophageal echocardiogram has played a key role in the diagnosis. Medical therapy has been inadequate and so surgical removal has been performed. Unsuccessful medical therapy, a new episode of thrombosis, intracardiac permanent catheter infections and high risk of systemic and pulmonary embolism are indications for thrombectomy.