Within the past 15 years a new family of peptides has been identified, known as trefoil factor family (TFF) domain peptides; they are associated with mucin-secreting epithelial cells and synthesised predominantly in the gastrointestinal tract. They share a highly conserved physical structure, and their role in mucosal defence and healing is becoming increasingly clear; more recently a tumour suppressor function has been postulated. Outside the gastrointestinal tract, members of this group of peptides have also been identified in the normal hypothalamus and pituitary, and in normal breast tissue where it is responsive to oestrogen stimulation. Evidence of peptide expression has been found in a range of urological, gynaecological, gastrointestinal, pulmonary and breast carcinomas, and in the last two it appears to carry prognostic significance. The present review aims to summarise the rapidly expanding data on the role of these peptides in epithelial inflammation, repair and neoplasia.