Bioactive peptides originated from casein and whey proteins make the majority of bioactive substances presentin dairy products. They are fragments obtained by degradation of protein that consisted of 3 to 20 amino acids and are synetised in the food digestion process in human body or during milk processing. In spite of milk being a great source of proteins, most bioactive peptides present in milk are in an inactive form within the native protein sequence and can be activated only by hydrolysis of the protein they originate from. Fermented milks and cheeses represent one of the main sources of bioactive peptides among commercially used dairy products. They can be a good source of antihypertensive, antithrombotic, opioid, antimicrobial, immunomodulatory and antioxidant peptides as well as mineral-binding peptides. Amino acid composition and sequences determine biologcal activity of bioactive peptides and mentioned peptides can have a positive influence on vascular, nervous, immune and digestive system. The aim of this paper is to give the overview of the most important bioactive peptides from the milk and dairy products, describe their biological activity in human organisam and the ways they are formed.