Trimeric sialic acid [Neu5Ac α(2→8)Ncu5Ac α(2→8)Ncu5Ac. 1] residue-containing gangliosides, GT4, α(2→6)GT4 and GT3, have been synthesized for the first time. Methyl [phenyl 5- acetamido-8-O-[5- acetamido-8-O-(5- acetamido-4,7,8,9-tetra-O- acetyl-3,5-dideoxy- d- glycero-α- d-galacto-2- nonulopyranosylono-1″,9′-lactone)-4,7-di-O- acetyl-3,5-dideoxy- d-glycero-α- d-galacto-2- nonulopyranosylono-1′,9-lactone]- 4,7-di-O- acetyl-3,5-dideoxy-2-thio- d-glycero- d-galacto-2- nonulopyranosid]onate ( 3) was prepared from 1, via lactonization, methyl esterification of the carboxyl group at the reducting end, O-acetylation and conversion of the anomeric acetoxy group into a phenylthio group. Iodonium-promoted glycosylation of 3 with 2-(trimethylsilyl)ethyl 2,6- di-O- benzyl-β- d- galactopyranoside ( 5), 2-(trimethylsilyl)ethyl 3-O- benzyl-β- d- galactopyranoside ( 6), 2-(trimethylsilyl)ethyl 2-O- benzoyl-3-O- benzyl-β- d- galactopyranoside ( 9), and 2-(trimethylsilyl)ethyl 2,3-di-O- benzyl-β- d- galactopyranoside ( 11) gave the corresponding tetrasaccharides ( 13–15, 17) having the (Neu5Ac) 3-Gal structure. The peracylated oligosaccharides 18 and 24 derived from 13 and 17, and the previously reported lactose derivative 29 were converted into the α-trichloroacetimidates 20, 26 and 31, and coupled with (2 S,3 R,4 E)-2-azido-3- O-benzol-4-octadecene-1,3-diol ( 21) to afford the corresponding β-glycosides 22, 27 and 32. These protected azidosphingosine derivatives were each transformed into the target gangliosides GT4, α(2 → 6)GT4 and GT3 via selective reduction of the azido group. subsequent coupling with octadecanoic acid, O-deacylation and saponification of the methyl ester and lactone groups.