Hypoalbuminemia occurs frequently in the course of wasting disease but never progresses to a condition of complete analbuminemia. The latter, in fact, is unknown in pathology. Analbuminemia, however, has been described as a benign congenital syndrome occurring in siblings (1-3). The absence of serious pathological changes in these two cases is striking and makes it appear likely that this form of benign analbuminemia belongs to the realm of congenital aberration of protein metabolism.The absence of circulating albumin creates a unique basal condition which makes it easy to follow the fate of infused albumin by more than one method. It was decided, therefore, to study the rate of disappearance of albumin in one of the siblings (a female) and to use for this purpose both I131-labeled albumin and a commercial human albumin. The rate of disappearance of the former was obtained by measuring the decay of radioactivity in the usual manner and of the latter by means of paper electrophoresis and immunological tests.