Chronic thromboembolic pulmonary hypertension is due to unresolved or recurrent pulmonary embolism. In the United States the estimated prevalence is 0.1-0.5% among survived patients with pulmonary embolism. The survival rate at 5 years was 30% among patients with a mean pulmonary artery pressure > 40 mmHg at the time of diagnosis and only 10% among those with a value > 50 mmHg. The interval between the onset of disturbances and the diagnosis may be as long as 3 years. Doppler echocardiography permits to establish the diagnosis of pulmonary hypertension. Radionuclide scanning determines whether pulmonary hypertension has a thromboembolic basis. Right heart catheterization and pulmonary angiography are performed in order to establish the extension and the accessibility to surgery of thrombi and to rule out other causes. The surgical treatment is thromboendarterectomy. A dramatic reduction in the pulmonary vascular resistance can be achieved; corresponding improvements in the NYHA class--from class III or IV before surgery to class I-II after surgery--are usually observed. Patients who are not considered candidates for thromboendarterectomy may be considered candidates for lung transplantation.