Abstract A preparative method for the isolation of oligosaccharide peptides from lysozyme digests of Micrococcus lysodeikticus cell walls is described. The method involves chromatography on Dowex 1, gel filtration on Bio-Gel P-4 columns, and chromatography on Dowex 50. Four glycopeptides designated as GP-1, GP-1a, GP-2, and GP-4 were isolated and their structures investigated by chemical and enzymatic techniques. GP-2 which comprises about 2% of the weight of the wall, is a disaccharide pentapeptide of the following structure, where Mur stands for muramyl. [see PDF for structure] GP-4, present in smaller amounts, possesses the same structure as GP-2, with the exception of the acetyl group on muramic acid. GP-1 is a dimer of GP-2 in which the peptide moieties are linked by a peptide bond formed between the COOH-terminal alanine of one peptide chain and the e-amino group of the lysine of a second peptide chain. GP-1a, present in very small amounts, is apparently a tetrasaccharide pentapeptide, the tetrasaccharide moiety of which is identical with the cell wall tetrasaccharide GlcNAcβ(1 → 4) MurNAcβ(1 → 4) GlcNAcβ(1 → 4) MurNAc; the peptide moiety linked to the muramic acid forming the terminal reducing end of this tetrasaccharide is identical with the peptide moiety of GP-2. In addition, small amounts of an unusual disaccharide, Glc-NAcβ(1 → 4) Mur, have also been isolated.