Chronic thromboembolic pulmonary hypertension (CTEPH) is an uncommon disease that is the most serious complication associated with unresolved pulmonary embolism. This disease has several risk factors, but no familial pattern has been described. Few thrombophilic conditions have been reported to increase risk of CTEPH, and none of the hereditary thrombophilias causes this disease. The reason CTEPH develops in some patients after pulmonary embolism remains unknown. We describe a 54-year-old woman and her maternal aunt who both underwent pulmonary thromboendarterectomy for CTEPH. This represents the first description of familial CTEPH.