Much research has been carried out on casein-derived bioactive peptides that are encrypted within the primary Structures of intact casein. Casein peptides are not active within the parent protein but can be released and activated during enzymatic hydrolysis, microbial fermentation and during gastrointestinal digestion. Once absorbed, casein peptides have potential to exert numerous biological effects in the body. These bioactive effects are being exploited by the food industry. Important tasks for the production of functional foods containing bioactive peptides are to either enhance their bioavailability from their natural source or create novel foods via the addition and/or fortification of isolated or enriched fractions of bioactive peptides. In this review. selected biological effects of casein-derived bioactive peptides, their application in industry, in addition to safety aspects and regulations relating to the use of these peptides, will be discussed. (C) 2009 Elsevier Ltd. All rights reserved.