Most human milk oligosaccharides (HMO) are resistant to digestion and absorption within the small intestine and reach the infant colon, where they can act as prebiotics that stimulate the growth of beneficial micro-organisms such as various species of Bifidobacterium. They can also act as receptor analogues that inhibit the attachment of harmful micro-organisms to the infant's colonic mucosa. A small part of the milk oligosaccharides are absorbed intact into the circulation and it has been hypothesised that these may act as immunomodulators. It is generally believed that bovine milk oligosaccharides are not absorbed by human adults or infants, thus making them available to be utilised as prebiotics or anti-infection materials. This book presents and discusses research on milk oligosaccharides.