Long-term pulmonary function in HLT is well preserved with no evidence of functional decline as a result of transplant "aging," providing the allografts remain free of complications. Long-term survivors with OB appear to be able to maintain adequate oxygenation despite the marked alterations of pulmonary function. The ability to preserve gas exchange at reasonable levels of oxygenation may be the factors permitting extended survival with OB for mean periods of 36.0 months or greater. Preliminary studies suggest that a declining FEF50/FVC, at a time when pulmonary function is normal, may be an index of impending airway disease. Physiologically, from a long-term point of view, HLT remains a viable option for selected patients with end-stage cardiopulmonary disease.