The authors describe a patient with chronic thromboembolic pulmonary hypertension. At pulmonary angiography, only severe hypertension with pruning of peripheral vessels was seen; the right pulmonary artery appeared normal. Despite the limited use of a nonionic contrast material, the patient died 11 hours after the study. At autopsy, a laminated well-organized thrombus that occupied virtually all of the right pulmonary artery and adhered to the vessel wall was seen. Other modalities should be investigated to help establish the diagnosis of chronic thromboembolic pulmonary hypertension.