Polyamines appear to be involved in the turnover, growth and maintenance of intestinal mucosa integrity. Since polyamines could act -in part at least- through their incorporation into cellular proteins as catalyzed by transglutaminase, we have measured this enzyme activity in villus enterocytes isolated from pig jejunum and in homogenate derived from isolated cells. A part of putrescine, spermidine and spermine taken up by enterocytes is incorporated in TCA precipitable material derived from cells and this corresponds to the presence of transglutaminase activity in cellular homogenates. This activity which is time and substrate concentration dependent is strongly inhibited by the transglutaminase inhibitor glycine methyl ester. The capacity for de novo production of polyamines from L-arginine or L-glutamine is very limited in isolated enterocytes, and this coincided with a very low ornithine decarboxylase activity when compared with polyamine cell content. It is concluded that the main source of polyamines for pig enterocytes is extracellular and that exogenous polyamines are substrates for enterocyte transglutaminase.