A 75-year-old man complaining of dyspnea and having sings of postcapillary pulmonary hypertension was diagnosed as pulmonary veno-occlusive disease and confirmed at autopsy. This is the oldest case ever reported. Almost all the small veins 2 mm or less in external diameter were partially or nearly completely occluded by intimal fibrous tissue, and the obstructive changes in the pulmonary arteries were much more limited. Pulmonary veno-occlusive disease is a rare, almost inevitably fatal disease of unknown etiology which has only recently been separated clearly from primary pulmonary hypertension as a distinct entity. Chest roentgenogram finding suggesting postcapillary pulmonary hypertension is a clue to a diagnosis and differentiates this from two other causes of clinical primary pulmonary hypertension, that is, recurrent pulmonary embolism and plexogenic pulmonary arteriopathy.