Milk is well-known for being an excellent source of proteins for humans. Besides caseins and whey proteins that represent 80 and 20% of the protein in bovine milk respectively, more than a hundred of minor soluble proteins like enzymes, growth factors, hormones or proteins from the milk fat globule membrane have also been reported. Milk also contains peptides that are produced by endogenous proteases such as plasmin and cathepsin D. After ingestion, milk proteins are degraded in the stomach and small intestine generating the release in the gut lumen of thousands of peptides. Some of them are known to exert biological activities i.e. antihypertensive, antimicrobial, immunomodulating, antioxidant activities etc. The release of bioactive peptides in vivo during milk digestion will be presented. In a first experiment, 6 multi-cannulated minipigs were fed 6 dairy products of identical composition but different structure (liquids vs gels). Effluents were collected over 5h and characterized using mass spectrometry showing that the bioactive peptide pattern was highly dependent on the food structure ingested. Then, sixteen human volunteers equipped with a naso-jejunum probe were fed either caseins or whey proteins. Effluents were collected from their small intestine over 7h and analysed by mass spectrometry. More than 16000 peptides were unambiguously identified, some of them being known for being bioactive. The concentration of 5 anti-hypertensive and opioid peptides in the small intestine was assessed and was found to be higher than that necessary for exerting a biological activity. However, for exerting their biological functions, these peptides would have to pass through the epithelial barrier and only scarce study have been published on the absorption of milk bioactive peptides by physiologically-relevant approaches. Therefore, the last experiment that will be presented consisted in investigating the absorption of milk peptides by Ussing chambers. A piece of pig jejunum was placed in the system and in vitro digested whey proteins were applied to the apical chamber and their passage through the epithelium was monitored over 2h by mass spectrometry. Results showed that many peptides, even rather large, can pass through the epithelial barrier and reach the bloodstream. However, their concentrations in the baso-lateral chamber is low. Overall, this presentation will try to illustrate the current knowledge on the release of milk bioactive peptides during gastrointestinal digestion and their absorption.