In suckling rats, it has been established that oral administration of spermine, a dietary polyamine, at appropriate doses, induces all the modifications in the digestive tract that occur at weaning, namely, (a) in the intestine: variations in the specific activities of disaccharidases and peptidases, gene expression, the level of receptors to polymeric immunoglobulins (RPIs), tissue histology, and the intestinal permeability to macromolecules; (b) maturation of the intestinal immunological system, an observation confirmed in mice; (c) an increase in the specific activity of enzymes contained in the pancreas; (d) a change in the growth rate and biochemical properties of the liver, e.g., in the synthesis of RPIs. The mechanism of spermine action is partly understood. In the intestine, two phases of events have been recorded. The first phase consists of the desquamation of the epithelium resulting from an activation of apoptosis, probably induced by the entrance of spermine into the enterocytes. The second phase concerns a hormonal cascade in which adrenocorticotrophic hormone, cytokines, bombesin and corticosterone intervene. A general hypothesis taking into account all the results obtained until now is presented as well as other observations recorded on the effect of exogenous spermine on the intestinal maturation of vertebrates other than the rat. (C) 2000 Elsevier Science B.V.