We report a 71-year-old man with right heart failure due to chronic pulmonary thromboembolism. Oral medications failed to control the condition but he was later successfully treated with intermittent administration of a PDE-III inhibitor for 2 years. Such therapy did not result in exacerbation of right heart failure but improvement of ANP/BNP levels to 32/104 pg/ml from a pretreatment value of 61/158 pg/ml, although no improvement was noted in pulmonary artery pressure or cardiac index. Intermittent administration of PDE-III inhibitors is a useful treatment for patients with right heart failure resistant to oral agents.