A method is described for estimating the quantity of blood in the leg. Experiments evaluating the accuracy and validity of the method using I131labeled human serum albumin and in vivo analysis are presented. The data suggest that in the recumbent position the leg is about 5.6 volumes per cent blood. Speculation in regard to the similarity and amount of other portions of the body to the leg lead to the possibility that about six-tenths of the blood is present in the carcass and four-tenths in the viscera.