Admitting the rarity of occurrence, Brill and Robertson1 called attention to what may prove to constitute a clinicopathologic entity, namely, subacute cor pulmonale. The features of this condition, according to their case report and to 2 similar ones that they were able to find in the literature, differ rather sharply from those of the acute and chronic forms of cor pulmonale. The acute form, confined practically to pulmonary embolism, is rarely associated with right ventricular hypertrophy. The chronic primary type2 includes pulmonary stenosis and insufficiency, pulmonary endarteritis, organic tricuspid insufficiency, mitral stenosis, diffuse pulmonary fibrosis3 and pulmonary emphysema. In the latter group the clinical course is usually protracted, right ventricular hypertrophy and dilatation are usually marked, and the cause is often clinically apparent. The subacute variety is characterized by a fairly rapid (nine days to two months) development and termination of signs and symptoms of strain of