We report a case of pulmonary embolism in a young man 39 years old, without obvious risk factors, who was presented to the hospital with symptoms and clinical findings suggestive of pulmonary embolism, due to deep venous thrombosis of lower extremities. Serial echocardiographic studies revealed a large, long mobile thrombus in the right atrium, which was finally thrown into the pulmonary circulation. Despite this new embolic episode the patient remained at the same clinical status, and hemodynamically stable without a further deterioration in his respiratory function. The contribution of echocardiography in the diagnosis of pulmonary embolism and current treatment options are discussed. Pneumon 2006, 19(1):65-73.