TFF1/pS2, TFF2/SP and TFF3/ITF are soluble peptides with trefoil domain (s) and C-terminal dimerization domain, which are conserved among human, cow, mouse and rat. TFF1 mRNA is expressed in stomach (mucous cells in fundus and antrum), TFF2 mRNA in stomach (mucous neck cells in fundus and basal cells in antral and pyloric glands) and duodenum (Brunner's gland), TFF3 mRNA in small intestine and large intestine (goblet cells). Expression of TFF1, TFF2 and TFF3 mRNAs are differentially regulated by FGF2/bFGF, FGF7/KGF, estrogen, aspirin, arachidonic acid, X-ray irradiation, and hydrogen peroxide. Gastric cancer is classified into the intestinal type and the diffuse type. TFF mRNAs are preferentially expressed in diffuse-type gastric cancer cells. Custom-made microarray (TFF mRNAs) and ELISA (TFF proteins) might be applicable for screening methods of peritoneal and bone marrow dissemination from diffuse-type gastric cancer. TFF1 and TFF2 mRNAs are frequently down-regulated in intestinal-type gastric cancer. TFF1 gene, inactivated by deletion, missense mutation and promoter hypermethylation, is a tumor suppressor gene implicated in gastric cancer. TFF2 is a candidate tumor suppressor gene; however, genetic and epigenetic alterations of TFF2 gene in human gastric cancer remain unclear. TFF1, TFF2 and TFF3 play key roles in mucosal protection through mucous-barrier formation, and also in mucosal repair through promotion of restitution after injury. Patients with chronic atrophic gastritis and those with ulcerative colitis are at risk of gastric cancer and colorectal cancer, respectively. TFF1, TFF2 and TFF3 proteins might be applicable for chemoprevention of gastrointestinal cancer associated with chronic persistent inflammation.