Homotransplanted canine livers can survive in recipient dogs for as long as 3 weeks.10,11 Evaluation of liver function and other tissue metabolism can be made during this time. Studies of this kind may lead to a better understanding of the homograft rejection mechanism. Previous histological and biochemical studies in dogs following total homotransplantation of the liver have shown a marked proliferative cellular response in the organs and a progressive obstructive jaundice pattern in the blood. Total serum protein and albumin levels as well as albumin-globulin concentration showed no marked alterations as determined by ordinary laboratory methods.11 When paper electrophoretic analyses were done, a fall in albumin and a rise in α2-globulin were most characteristic.10 The availability of radioisotopic techniques for studying plasma protein metabolism prompted the present study with 2 objectives in mind: (1) to determine the rate at which the homotransplanted liver synthesizes individual