To evaluate the effect of an elevation in systemic arterial pressure upon pulmonary blood flow and arterial oxygenation during right ventricular hypertension (RVH), we acutely studied 13 1-d-old piglets. Catheters were positioned in the pulmonary artery, both atria, and the aorta for hemodynamic measurements. An electromagnetic probe was positioned in the main pulmonary artery for pulmonary blood flow measurement. Systemic and regional blood flow were measured with the radiolabeled microsphere technique. A balloon-mounted catheter was advanced in the aorta and maintained at the lower thoracic level. After induction of RVH (pulmonary artery banding), a significant decrease in arterial O2pressure from 54.4 ± 1.6 to 10.6 ± 0.4 kPa (p< 0.01), a 30% reduction in systemic arterial pressure, and a 44% decrease in pulmonary blood flow were observed. During RVH, partial inflation of the aortic balloon to restore the systemic arterial pressure to its initial value led to an increase in arterial O2pressure to 23.5 ± 3.1 kPa (p< 0.01). Full inflation of the balloon further increased the arterial O2pressure to 32.6 ± 2.9 kPa (p< 0.01). Aortic balloon inflation increased pulmonary blood flow in 11 and systemic O2delivery in nine of the 13 animals. RVH was associated with a significant increase in cerebral and right ventricular myocardial free-wall blood flow and a decrease in renal and bowel blood flow and O2delivery (p<0.01). Aortic balloon inflation during RVH did not change either the cerebral or myocardial free-wall blood flow, but further significantly decreased renal and bowel blood flow and O2delivery. In conclusion, an elevation in systemic arterial pressure significantly reduces foramen ovale shunt and increases pulmonary blood flow and systemic O2delivery in the newborn pig with RVH. This finding may prove useful in the clinical management of hypoxemic infants with persistent pulmonary hypertension syndrome.