THE presence of fucose as a constituent sugar in oligosaccharides obtained from human milk was reported by Kuhn1 in 1952. Since that time Kuhn and his associates have characterized four oligosaccharides from this source, in all of which fucose is found: a trisaccharide, fucosido-lactose; two pentasaccharides referred to as lacto-N-fucopentaoses I and II, and a hexasaccharide, lacto-N-difucohexaose; the last three are derivatives of a common, fucose-free parent compound—lacto-N-tetraose2. Montreuil, in a series of communications, has reported the occurrence of compounds probably identical with those analysed by Kuhn, and in addition, a further range of fucose-containing substances of still greater complexity3. He has isolated thirteen sugar compounds, other than lactose, from human milk, all of which contain galactose and glucose and most of them fucose and acetylglucosamine as well.