Right heart catheterizations were performed in 56 sessions on 25 reindeer with determinations of blood pressure and oxygen saturation. Cardiac output was calculated from cineangiocardiograms. When the animals were placed in prone position, heart rate was about 50/min, mixed venous blood oxygen saturation 68 to 72%, right ventricular systolic pressure 27 mmHg, pulmonary arterial pressure 25/16/11 mmHg, pulmonary arterial wedge pressure 6--8 mmHg and pulmonary transfer time 4 to 5 cardiac cycles. When the animals were placed on their side, the heart rate rose to 90 b/min, mixed venous blood oxygen saturation decreased by about 4% and the right ventricular and pulmonary arterial pressures increased by about 10 mmHg; pulmonary arterial wedge pressure did not change. Hypoxemia led to an increase in heart rate, cardiac output and pulmonary arterial pressure; the latter two measures tended to increase whenever the heart rate increased. Under the conditions stated here, an increased pulmonary vascular resistance was calculated when pulmonary arterial pressure was increased.