In clinical lung allotransplantation, the recipient's remaining diseased lung has caused severe ventilation perfusion imbalance in the graft. We have performed one-stage bilateral lung replantation on 26 dogs as a prototype for possible future solution of this physiologic problem. Pulmonary edema was the main cause of death. Ten dogs lived more than 1 month after operation; seven are still alive and vigorous up to 6 1/2 months. X-ray films of the chest, pulmonary arterial pressures, angiograms, and blood gas levels are normal. Conclusions are that (1) pulmonary edema is proportional in severity to the degree of anoxic damage to the graft, and is potentially reversible; (2) one-stage total pulmonary denervation is readily tolerated by the dog; and (3) simultaneous bilateral lung replantation with long-term survival and nearly normal dynamics of ventilation and pulmonary circulation is feasible.