The pathophysiology and treatment of pump failure with right ventricular overload due to chronic pulmonary diseases were discussed. When right ventricular overload occurs hypertrophy and dilatation of right ventricle follows and the heart as a whole, including left ventricle, is altered in morphology and function .Therapeutic measures for right ventricular overload are the key to management and treatment of pump failure. Pulmonary hypertension, as an etiological factor, is discussed and is divided into two categories, that is, mild to moderate pulmonary hypertension with hypoxia due to chronic obstructive lung disease, and severe pulmonary hypertension due to pulmonary vascular disease. In each category, effects of oxygen inhalation and vaso-dilating agents were evaluated. Oxygen did not decrease pulmonary vascular resistance in the state of chronic hypoxia, though a vasodilating agent was effective. In pulmonary vascular disease, vaso-dilating agents were effective to decrease pulmonary vascular resistance and pulmonary artery pressure, though the effect was less than 30% down in resistance.