To evaluate the putative importance of digestive luminal polyamines, we investigated the role of oxidation in putrescine uptake and transport in differentiated Caco-2 cells grown in monolayer.Our results confirm a putrescine uptake system located both at the apical and basolateral cell membrane. Putrescine is efficiently transported and excreted in the apical-to-basolateral direction.These results suggest (i) a diamine oxidase controlled catabolic oxidative excreting pathway and (ii) a paracellular route for putrescine transport. This catabolic route seems to proceed by converting putrescine into gamma-aminobutyraldehyde which is then rapidly excreted from the cell at the basolateral membrane since no gamma-aminobutryraldehyde was detected in the cell. This putative basolateral excreting mechanism is inhibited in the presence of the diamine oxidase inhibitor, aminoguanidine.