49-year-old male with severe biventricular dysfunction and evidence of multiple pulmonary emboli was found by two-dimensional echocardiography to have a freely mobile, serpentine-like mass within his right atrium. This mass was seen to prolapse in diastole through the tricuspid valve into the right ventricle and was considered to represent a thrombus. He was given 96 h of intravenous streptokinase therapy. Serial two-dimensional echocardiography demonstrated dissolution and eventual disappearance of the thrombus from the right atrium and right ventricle. During and after streptokinase therapy there was no evidence of further pulmonary embolization.