Active transport of sodium taurocholate was demonstrated in the following species: albino mouse, golden hamster, squirrel monkey, king pigeon, and Leghorn chicken. The criterion for active transport was the ability of everted gut sacs to establish serosal: mucosal concentration gradients greater than unity In all cases, this activity was limited to the distal half of the small intestine. 2,4-Dinitrophenol inhibited taurocholate transport. These results are similar to those previously reported for tissue from rats and guinea pigs. In vivo studies were performed by introducing solutions of radioactive taurocholate into tied-off portions of the small intestine of anesthetized animals and determining the rate of appearance of the radioactivity in the bile collected from the common duct. The following species were studied: white rat, mongrel dog, spider monkey, and rabbit. In all cases the major transport activity was in the ileum.