Four unidentified acidic glycolipids (X3-X6) were isolated from the kidney of the Pacific salmon on an anion exchange column and by high performance liquid chromatography using a silica bead (Iatrobeads) column. Based on methylation analysis, chemical and enzymatic degradation, proton nuclear magnetic resonance spectroscopy and mass spectrometry, the glycon structure of X5 and X6 was identified as a unique disialosyl fucosyl-N-acetylgalactosaminyl ganglio-N-tetraose:Fucalpha3GalNAcbeta3Galbeta3GalNAcbeta4[NeuAcalpha8NeuAcalpha3] Galbeta4Glcbeta1Cer. NMR showed that X3 and X4 were analogues of X5 and X6 and contained O-acetyl groups on C4 of the outer N-acetylneuraminic acid, first disialosyl gangliosides containing 4-O-acetyl-N-acetylneuraminic acid. The ceramides of X3 and X5 contained predominantly C24: 1, and X4 and X6 contained saturated fatty acids (C14: 0, C16: 0 and C18: 0), whereas the long chain base was exclusively sphingenine. The concentrations of X3 and X4 were 0.13 and 0.16 nmol/g of kidney respectively and those of X5 and X6, were 0.07 nmol/g each.