T HE “mystery of car pulmonale,” as expressed by Cournand,” still awaits solution. Although a great deal of meritorious research work has been achieved during the last years, the pathogenesis of this condition is not yet fully understood, the criteria for early diagnosis are still inadequate, and the results of therapy are far from satisfactory. One of the multiple factors for this state of affairs is the close interdependence of respiratory and circulatory disturbances. paper by Wells4g deals with car pulmonale as a consequence of pneumoconiosis; the extensive material of McKeown30 and of K6nnz5 has been worked up only from the anatomic angle; Walzer and Frost’s publication48 includes only a little material without sufficient clinical detail. We hope, therefore, to fill a real gap by discussing some questions of pathogenesis and symptomatology derived from the study of our material consisting of 67 cases verified at necropsy in the course of the last four years. There is also a deplorable lack of agreement on terminology. Whereas to most authors car pulmonale means nothing more than right ventricular hypertrophy consequent to chronic bronchopulmonary disease, others include the notion of right heart failure in this term, although it would be more appropriate to apply the expression “car pulmonale decompensatum” or “car pulmonale with heart failure” to this latter condition. This disagreement on diagnostic criteria and terminology has led to further confusion since the data on this subject in the literature have been mostly derived from clinical material lacking homogeneity and adequate nosologic classification. The anatomic diagnosis of car pulmonale with heart failure has been based on (a) the presence of isolated hypertrophy and dilation of the right ventricle; (b) absence of any cardiac alteration that may account for this hypertrophy; (c) presence of chronic bronchopulmonary disease; and (d) congestion of parenchymatous organs. The clinical diagnosis has been confirmed at necropsy in each case. This shows that the differentiation of car pulmonale with heart failure from other forms of heart failure or from ventilatory insufhciency is well within our capabilities at least in this terminal stage, although the difficulties of early diagnosis have been rightly stressed.‘O fz6 Although morbid anatomy may solve these problems, this field of research has been sadly neglected during the last decade, while functional pathology has come into its own. To this branch of science we owe much remarkable information on the various aspects of car pulmonale. There are only a few studies based on necropsy material9 tz5 n30 e36 f4* The Italian authorsgs3’j have been exclusively concerned with cases of tuberculous origin; the PATHOGENESIS