We report a case of a 72-year-old woman with coronary artery disease in whom a thrombus in transit in the right atrium was diagnosed accidentally. After 72 hours of treatment with intravenous anticoagulants she developed a pulmonary thromboembolism resolved with systemic fibrinolysis. This is a rare case in which such a diagnosis preceded an embolic event. This fact raises the controversy about the best therapeutic management of this unusual form of thromboembolic illness.