CONSIDERABLE QUANTITIES Of enzyme protein from the salival T glands, stomach, and pancreas are normally secreted daily into the gut. Shed epithelial cells and mucus add to the total. Further, various components of the extracellular fluids are regularly transferred into the gut; albumin and other plasma proteins have been identified, by electrophoretic and other methods, in contents of the normal stomach, duodenum, and jejunum, and in saliva. Collectively, these proteins constitute a large and mobile pool which approximates 35-100 gin. per day. 16 This report concerns quantification of the plasma protein (particularly, albumin) component of this mixture in healthy subjects and in patients with excessive losses of these proteins via the gut. The abnormalities in this latter group are described as "exudative gastroenteropath y" and "protein-losing enteropathy" (PLE). In healthy adult man, the liver synthesizes albumin at the rate of 10-20 gin. per day. In the steady state an equal quantity is degraded or catabolized, Thus, turnover approximates 3-5% per day of the total exchangeable albumin (TEA) pool of about 300 gin. Transfer into the gut accounts for part of the total quantity catabolized normally, but the magnitude of this fraction is still in doubt. In man the liver can increase albumin synthesis only to a limited extent, ~ probably to no more than twice the normal rate. Continued daily losses in excess of about 10-30 gin. of albumin will eventually result in hypoalbuminemia and depletion of TEA, whether the "hypercatabolism " is the consequence of excessive loss into the urine, or into the gut, or rarely, excessive degradation by other means. Hypoalbuminemia may develop while there is a high intake