The objectives of this work were to study the FA composition of milk gangliosides, as well as to gain further insight into the characterization of human milk gangliosides. The potential capacity of human milk gangliosides to adhere to human enterotoxigenic Escherichia coli (ETEC-strains) was also studied. Human milk gangliosides were isolated and identified by high-performance TLC or immunoassay. The latter also was used to assay bacterial adhesion. The FA composition of gangliosides was studied by GC. The presence of O-acetyl GD3 (Neu5,9Ac2alpha2-8 NeuAcalpha2-3Galbeta1-4GlcCer) and trace amounts of GM1 [Galgamma1]3-3GalNAcgamma1,-3(Neualpha2-3)Galbeta1-4GlcCerl in human milk was confirmed. Medium-chain FA were almost absent in colostrum, whereas in the subsequent stages they rose to 20%. The levels of long-chain FA decreased after colostrum. With respect to the degree of saturation, gangliosides from colostrum were richer in monounsaturated FA than gangliosides synthesized during the rest of the lactation period, opposite to the pattern for PUFA. A human-ETEC colonization factor antigen II-expressing strain showed binding capacity to human milk GM3 (NeuAcalpha2-3Gal[1-4GlcCer). New data on human milk gangliosides have been gathered. A thorough knowledge of their composition is needed since they may have important biological implications in regard to newborns' defense against infection.