A haemodynamic examination of 10 dogs was carried out at rest, during volume loading and after ligation of the right coronary artery in the presence of a closed pericardium. Ligation of the right coronary artery led to haemodynamic signs of depression of right ventricular function--a drop in systolic pressure and an increase in end diastolic pressure, together with a shift of the functional curve to the right and downwards. Overall performance of the heart (cardiac output and the mean systemic pressure, also fell. Our results show that the depression of the systolic function of the myocardium in the presence of right ventricular infarction can be an important factor in the genesis of low cardiac output syndrome observed in clinical situations. Its pathophysiological mechanisms and some of the clinical consequences are discussed.