In this report we describe studies on the structures of the O-linked carbohydrate units in cell-surface glycoproteins of epimastigote forms of the G-strain of Trypanosoma cruzi. Mild alkaline reductive degradation of the 38/43 kDa glycoproteins resulted in beta-elimination of glycosylated threonine and/or serine residues, and the liberation of N-acetylglucosaminitol, galactobiosyl-, galactotriosyl-, galactotetraosyl- and galactopentaosyl-N-acetylglucosaminitol. The structures of these oligosaccharide alditols were established by n.m.r. spectroscopy and methylation analysis as: Galf beta 1-4(Galp beta 1-6)GlcNAc-ol; Galp beta 1-3Galp beta 1-6(Galf beta 1-4)GlcNAc-ol; [(Galp beta 1-3)(Galp beta 1-2)Galp beta 1-6](Galf beta 1-4)GlcNAc-ol; [(Galp beta 1-3)(Galp beta 1-2)Galp beta 1-6](Galp beta 1-2Galf beta 1-4)GlcNAc-ol.