Investigations were undertaken to obtain information on the mechanism by which orally administered spermine induces postnatal maturation in the rat intestine. Suckling rats ingested one dose of spermine (8 mumol) then were sacrificed at different intervals. -A. Proximal and distal parts of the intestine were homogenised. -B. A modification of the Wieser's technique was used to isolate cell fractions from the proximal mucosa. Wet weight and length of intestine; protein content, DNA amount, disaccharidase activity, polyamine amounts in intestinal and cellular extracts were measured. Spermine ingestion induced two phases of events: first, a cellular desquamation then a new cell differentiation. In the isolated epithelial cells, two and four hours after spermine ingestion, modifications in lactase and maltase specific activity were recorded, as were variations in spermine, spermidine and putrescine content. These observations clarify the cellular and molecular events of the intestinal development occurring after spermine ingestion and open new research perspectives.