The trefoil family of peptides is mainly associated with gastrointestinal tract. These peptides protect the mucous layer. The protective role of trefoil peptides is explained by their interaction with carbohydrates attached to mucin glycoproteins and by maintenance of the mucus structure. Trefoil peptides influence migration of epithelial cells and thus contribute to regeneration of the mucous layer. A correlation between trefoil peptides and oncogenesis remains unclear.