ALTHOUGH transplantation of canine lungs is technically possible and short term survival of a recipient animal is readily achieved, the functions of the homografted lung need careful study prior to clinical application of this modality. The lung serves as an excellent preparation for study, both for its ventilatory capacity and its respiratory capacity. Without sufficient functioning pulmonary tissue, death ensues within a very short time. The technique of homologous lung transplantation and the length of its survival have been intensively investigated. 3,6,7,9,10 The functions of the transplant have also been studied, but to a lesser extent. Neptune et al 9 noted that a homografted lung would function for half the time from transplantation until death. Patency of the transplanted pulmonary arterial tree has been demonstrated by angiography. 2,4 Faber et al 5 showed that the transplant had an adequate oxygen uptake using differential bronchospirometry. Alican and Hardy 1 reported an