We have previously shown that spermine, shortly after its ingestion, can induce the alteration of the morphology of the small intestine of suckling rats. It was proposed that this alteration is due to polyamine accumulation inside the epithelial cells. This could also be related to the fact that the intestine of the suckling rat is in an immature state. To shed light on this issue, disaccharidase and alkaline phosphatase activity assays, protein, DNA and RNA content measurements and polyamine concentration analysis were performed on the small intestine of suckling and weaned Wistar rats treated with spermine. Spermine did not induce the same intestinal alterations in weaned rats compared to suckling animals. Indeed, in sucklings, spermine administration induced a decrease of the protein, DNA, putrescine and spermidine intestinal content, suggesting a cell loss. The cell loss impaired the activity of intestinal enzymes: lactase, maltase and alkaline phosphatase. In weaned rats, the same treatment did not alter these parameters. Exogenous spermine by itself is not sufficient to induce the alterations described here and previously. The maturity degree of the small intestine could be the basis of this process.