Colostrum is the specialized milk produced for the first few days following parturition. It is much richer in immunoglobulins, antimicrobial peptides and growth factors than the subsequent mature milk. In this article, some of these constituents of human and bovine colostrum in comparison with mature milk are reviewed. Marked species differences exist in the constituents of both colostrum and mature milk. Recent studies suggest that colostral fractions, or individual peptides present within colostrum, might be useful for the treatment of a wide variety of gastrointestinal conditions including inflammatory bowel disease, non-steroidal anti-inflammatory drug-induced gut injury and chemotherapy-induced mucositis. The relative merits of using colostral fractions as opposed to an individual recombinant peptide for the treatment of these various conditions are discussed.