Small intestinal transplantation has had several clinical attempts based on extensive experimental work during the past two decades. Several models, such as auxiliary (heterotopic) or orthotopic models, have been developed in regard to problems with graft immunology and function. The question of mesenteric-portal or mesenteric-caval graft drainage was raised, and the answer seems to be open. Concerning lipid absorption, interest was directed to the reconstitution of lymphatic vessels, because orally administered cyclosporine A is absorbed by the lipid mechanism. Carbohydrate digestion and absorption are used for determination of graft function and for monitoring graft rejection. This article summarizes these problems and deals with the surgical procedure of small bowel transplantation in the rat.