Abstract Lung transplantation is now a clinical reality in adults but is limited by the scarcity of appropriate donors. The donor shortage is even more acute for neonatal and pediatric patients. Reduced-size lung grafts would expand the pool of appropriate cadaveric donors and allow HLA-matched living related lobar or segmental lung transplants. To evaluate this experimentally, we developed a model of pulmonary lobar transplantation in neonatal pigs and studied the acute hemodynamic response after transplanting the left lower lobe from a more mature donor to a neonatal recipient. Technical considerations included using the recipient atrial appendage for the pulmonary venous anastomosis. Nine pairs of pigs underwent left lateral thoracotomy. The recipient left atrial and pulmonary arterial pressures, cardiac output, and pulmonary vascular resistance were measured before pneumonectomy and after left lower lobe transplantation. Although the left atrial and pulmonary arterial pressures remained unchanged after transplantation, there was a 15% increase in pulmonary vascular resistance and a 23% reduction in cardiac output. Neither change was statistically significant. The distribution of blood flow through the left and right pulmonary arteries was unchanged after transplantation. We conclude that lobar transplantation is technically feasible in immature animals and that the pulmonary venous anas tomosis to the left atrial appendage facilitates the procedure. This model may prove useful in studying lung transplantation in immature recipients and expedite implementation of reduced-size lung transplantation in neonatal and pediatric patients.