Human milk fat globule membranes have been prepared according to Brunner's procedure : isolation of the cream by low speed centrifugation, three washings by 0.25 M saccharose containing 0.002 M MgCl 2 , freezing and thawing, vigourous shaking, washing and lyophilisation. 900 mg of membranes are obtained from 1 liter of milk. Glycosphingolipidic fractions are isolated by the Folch method : extraction by chloroform methanol (2 : 1 and 1 : 2, v : v), then partition by adding 0.2 volume of water. The two phases are further purified by Sephadex LH 20 chromatography, leading to the « Purified aqueous phase(15 to 20 mg per liter of milk) and to the « Organic phase . The « Purified organic phase(20 to 25 mg per liter of milk) is obtained after a further purification on silicic acid column (Biosil A) to eliminate the neutral lipids. Purity of the various fractions has been checked by thin layer chromatography ; compounds are revealed by either orcinol, resorcinol or molybdic acid reagents. In addition, absence of milk oligosaccharides has been checked by reduction with tritiated sodium borohydride. The carbohydrate content has been determined by colorimetric methods and the molar ratio has been obtained by gas liquid chromatography of the trifluoroacetylated methylglucosides. The results are as follow (per cent of dry weight) : « Purified organic phase: galactose + glucose : 4.2, N -acetylglucosamine : 0, N -acetylneuraminic acid : 0 ; « Purified aqueous phase: galactose + glucose + fucose : 9.1, N -acetylglucosamine : 1.4, N -acetylneuraminic acid : 3.5. The composition in sphingosine and sphingosine derivatives has been determined after hydrolysis and further identification by thin layer chromatography. The carbohydrate moieties of glycosphingolipids have been cleaved from the ceramides according to Hakomori's procedure : periodic oxidation (catalyzed by osmium tetraoxyde) of the acetylated glycosphingolipids. After deacetylation and purification on Dowex 50 × 8 resin, the obtained mono- and oligosaccharides have been identified by paper chromatography, by determination of the reducing end and by the study of the oligosaccharides liberated after partial hydrolysis. From the « Purified organic phasewe obtained lactose only, and from the « Purified aqueous phasewe obtained : lactose, fucosidolactose, lacto- N -fucopentaose I,lacto- N -difucohexaose and neuraminyl-lactose. This results exclude the possibility that milk oligosaccharides are generated from the catabolism of the glycosphingolipid from milk fat globule membranes. In fact, the carbohydrate moieties of glycosphingolipids is only a few per cents in weight of the total milk oligosaccharide content (7 to 12 g per liter). However, one may consider that the metabolism of the carbohydrate moieties of glycosphingolipids is correlated with the metabolism of blood group substances in a process involving glycosyltransferases and lactose as acceptor. Les fractions glucidiques des glycosphingolipides extraits des membranes isolées des globules lipidiques du lait de Femme ont été détachées des céramides par le procédé de Hakomori et identifiées au lactose, au fucosido-lactose, au lacto- N -fucopentaose I, au lacto- N -difucohexaose et au neuraminyl-lactose. Tous ces glucides sont des constituants du « gynolactosede M. Polonovski et A. Lespagnol. Cependant, nous pouvons exclure l'hypothèse que les oligosaccharides du lait de Femme proviennent du catabolisme des glycosphingolipides des membranes des globules. En effet, plusieurs dizaines d'autres oligosaccharides existent dans le lait de Femme qui ne sont pas des constituants des glycosphingolipides des globules lipidiques. En outre, les glycolipides ne représentent qu'une masse très faible en regard de celle des oligosaccharides du lait de Femme dont le taux varie entre 7 et 12 g p. litre.