This case report describes a 40-years-old man affected by fracture of leg and pulmonary embolism. Two-dimensional echocardiography showed a large right atrial migrant thromboembolus prolapsing into tricuspid valve during diastole. The patient was treated with rt-PA through right atrial venous catheter and underwent to serial echocardiographic examinations. The rt-PA determined the dissolution of the thrombo-embolus at the 2nd hour of infusion. It is concluded that early two-dimensional echocardiography might be a very helpful technique to diagnose and follow-up therapy of pulmonary embolism.