Pathologic involvement of the left ventricle in chronic cor pulmonale. To determine whether or not the left ventricle is pathologically involved in patients with chronic cor pulmonale, right and left ventricular weights, wall thickness, myocyte diameters, and percentage of fibrosis in 18 autopsied hearts were examined in patients with chronic pulmonary disease (CPD); ten had right ventricular hypertrophy on their electrocardiograms, and eight were without right ventricular hypertrophy. Five with extracardiopulmonary disease were used as controls. The weight of the right ventricle was significantly increased in CPD when compared to control subjects. Walls of both ventricles were significantly thicker in CPD. Myocyte diameters of both ventricles were significantly greater in CPD. The percentage of fibrosis in the right ventricle was significantly greater in CPD. The percentage of fibrosis in the left ventricle was significantly greater only in patients with right ventricular hypertrophy. We concluded that the left ventricle was also involved pathologically in patients with chronic cor pulmonale in the end stage of the disease. 