Interest in the intestinal absorption mechanisms of drugs has increased because transepithelial passage across the gut does not necessarily follow a passive diffusion process. Amoxycillin, like other amino-beta-lactam antibiotics, has been demonstrated in vitro to use the dipeptide carrier-mediated system in rodent small intestine. In order to assess the in-vivo relevance of these data, we applied the Loo-Riegelman method for a reappraisal of amoxycillin absorption kinetics in healthy human volunteers. The results showed evidence of a saturable carrier-mediated uptake of this antibiotic. With respect to the in-vitro data previously published, the dipeptide carrier system would appear to be the most likely transport mechanism.