Background: Chronic myeloproliferative disorders (CMPD) seem to be associated with an increased risk for pulmonary hypertension (PH). Case Report: A patient with history of chronic idiopathic myelofibrosis (CIMF) presented with progressive dyspnea (New York Heart Association class III). Until this time he had not received specific treatment for CIMF. Echocardiography and right-heart catheterization confirmed PH. Further diagnostic procedures excluded a specific cause of PH. Therefore, primary PH was assumed. 2 years later he presented again with progressive dyspnea due to a progress of PH. A few days later the patient died from acute posterior myocardial infarction. Pathologic examination of the lung showed an obstruction of the small vessels by conglomerates of megakaryocytes. Discussion: We conclude that PH developed secondarily due to CMPD. PH should be suspected in patients with CMPD and should influence the decision for treatment of CMPD.