It is known that uptake of di- and tripeptides by distinct peptide transport systems is an important biological process by which amino acids are absorbed from the gastrointestinal tract (Rubino et al 1971; Webb and Bergman, 1991). However, until recently it was generally accepted that absorbed peptides had to be completely hydrolysed in to free amino acids within the enterocyte (Krzysik and Adibi, 1977) prior to their transport into the circulation. Nevertheless, it has been suggested that, in ruminant species at least, a substantial proportion of the total amino acid uptake from the gastrointestinal tract may be in the form of peptides (Webb, 1990; Seal and Parker, 1991; Webb and Bergman, 1991) and that a large part of this absorption may occur across the stomach region (i.e. rumen and omasum) (Webb, 1990). Consequently, the present study was designed to assess the uptake of amino acids in the form of low molecular weight peptides across the gastrointestinal tract of growing lambs.