The intestinal metabolism and absorption of enterostatin was studied using brush-border membrane vesicles and an in vitro model of intestinal segments from rabbit ileum mounted in Sweetana-Grass diffusion chamber. Hydrolysis of enterostatin was observed with both epithelial sheets and brush-border membranes. The main metabolite was found to be des-arginine-enterostatin. Dipeptidylpeptidase IV was found to play a minor role in enterostatin degradation, whereas carboxypeptidase P activity accounted for the initial step of peptide hydrolysis. More than 50% of the amount of enterostatin added to the mucosal compartment of the Sweetana-Grass diffusion chamber was degraded after 30 min. Enterostatin was mainly absorbed as degradation products but a small transepithelial passage of des-arginine-enterostatin and immunoreactive enterostatin was also detected. Although immunoreactive enterostatin exhibits a low apparent permeability coefficient in rabbit ileum, the luminal production of this peptide may be of physiological importance in the control of appetite.