Increased pulmonary arterial pressures as a result of pulmonary disease are described in two cows with chronic pneumonia and one cow with acute pneumonia. Based on clinical signs of congestive right heart failure, increased pulmonary arterial pressure, and right ventricular hypertrophy, cor pulmonale was diagnosed in one cow. Two cows had increased pulmonary arterial pressure and signs of right heart insufficiency, but right ventricular hypertrophy was not identified. Two of the cows had ventral edema and exercise intolerance. All cows had jugular venous distention and increased right atrial and pulmonary arterial pressures. Peripheral arterial PpO, was decreased in two cows, and not measured in the third cow. Although an uncommon cause of congestive heart failure in cattle at low altitudes, pulmonary hypertension should be considered in cattle with clinical right heart failure. (Journal of Veterinary Internal Medicine 1992; 6:214-219)COR PULMONALE refers to right ventricular hypertrophy or right heat? failure secondary to pulmonary hypertension.lr2 Cor pulmonale occurs when pulmonary hypertension caused by increased pulmonary vascular resistance increases the cardiac workload. This increased cardiac workload is responsible for the right ventricular hypertrophy and eventual congestive tight heart failure (CHF).3Increased pulmonary vascular resistance may occur in response to pulmonary vasoconstriction or a decrease in functional pulmonary vascular capacity. Alveolar hypoxia causes contraction of the precapillary pulmonary vessels, resulting in pulmonary hypertension.',2.4 Conditions that may induce hypoxia include: exposure to high altitude, respiratory impairment secondary to chest wall abnormalities, airway obstruction, pneumonia, pulmonary edema, emphysema, or pulmonary vascular disease.' At high altitudes, hypoxic pulmonary vasoconstriction/hypertension is a common cause of cor pulmonale (brisket disease) in cattle.1.2,6 Exposure to decreased ambient temperature also causes pulmonary From the