The stentless bioprosthesis is unique in that the glutaraldehyde (GA) -treated tissue is implanted in direct contact with the native aorta. In order to study this junctional area, sheep aorta treated with 0.625% GA were inserted in the descending aorta of 11 adult sheep and removed between four and 120 days after implantation. The junctions were evaluated histologically and by immunohistology. By day 60, the GA-treated conduits were calcified, and by days 60 and 120 the calcification had spread to the host aorta. The luminal and abluminal aspects of the junction were covered by host-derived tissue.