Availability of an isolated jejunal segment for perfusion in the management of chronic uremia makes it possible to study absorption and exchange of water, electrolytes, and important nutrients without contaminating gastric, pancreatic, and biliary secretions. This clinical investigative procedure has been described in detail previously, including review of the pertinent literature.6 It is the purpose of this paper to document an additional clinical experience with the procedure over a period of 3 years and 9 months, and to report further studies on some transfers in this isolated jejunum. The Isolated Jejunal Segment Repetitive measurements of the volumetric capacity of the segment, of rates of transfers of water, electrolytes, and crystalloids together with several barium contrast instillations over a 2½ year period has afforded some useful correlative information. The initial capacity of about 300 ml. decreased to about 100 ml. 2½ years later. This change was associated with roentgenographic evidence