A method of endothelial cell removal was developed to provide valved xenografts with reduced immunity, yet durability comparable with that of homografts. Adult porcine valved pulmonary conduits were isolated, washed and incubated in trypsin-EDTA solution. Endothelial cells were flushed free with culture medium, and the xenografts cryopreserved. Grafts were thawed after three months, and evaluated structurally. Gross examination of the grafts showed no cracks or other morphological damage. Light microscopy showed mildly edematous changes, with the elastic layers preserved. Incubation with trypsin-EDTA solution consistently removed the endothelial layer, without damaging the underlying tissues. In conclusion, it is possible to remove selectively the xenograft endothelium, leaving the underlying tissue intact. This may permit further structural manipulations that improve graft durability.