Successful small bowel transplantation is among the major unsolved goals in clinical surgery. The advent of Cyclosporin A, a powerful immunosuppressive agent is a hopeful development in this regard. This project is a methodical approach to small bowel transplantation in the laboratory, utilizing Cyclosporin in preparation for eventual clinical application. Even basic data pertaining to small bowel transplantation is sparse since graft prolongation beyond a few days could not be obtained with Imuran and Prednisone. Pilot studies in our own laboratory and in Canada indicate that meaningful small bowel graft prolongation can now be obtained with Cyclosporin A. In preparation for clinical application, considerable core information will be accumulated in the laboratory as outlined in this project. The facets of small bowel transplantation to be studied are: (1) Histological features and patterns of rejection; (2) Physiological parameters associated with functioning and rejecting transplants; (3) Cyclosporin dosage schedule and variations in trough blood levels; optimal routes of administration; (4) immunological features observable in our outbred system; (5) Usefulness of concurrent Prednisone usage and the desirable dosage; (6) Optimal method to treat rejection crises (steroid pulse, Cyclosporin pulse, ALG); (7) Observations in chronically surviving transplant animals for tumorogenesis and infection; (8) Exploration of ice flush storage of transplantable bowel and its time limitations; and (9) Technical variations such as the use of Roux-en-y loop for periodic biopsy, and of venous outflow anastomosis to the vena cava rather than portal vein.