Two positional isomers of sialyloligosaccharides were isolated from the urine of a patient with adult type sialidosis with partial deficiency of beta-galactosidase. From structural studies including sugar analysis, enzyme degradation and methylation analysis, the following structures are deduced; 1. alpha-AcNeu-(2 leads to 3)-beta-Gal-(1 leads to 4)-beta-GlcNAc-(1 leads to 2)-alpha-Man-(1 leads to 3)-beta-Man-(1 leads to 4)-GlcNAc 2. alpha-AcNeu-(2 leads to 3)-beta-Gal-(1 leads to 4)-beta-GlcNAc-(1 leads to 2)-alpha-Man-(1 leads to 6)-beta-Man-(1 leads to 4)-GlcNAc The sialyloligosaccharide 1 has previously been reported to be present in liver and urine of patients with mucolipidosis I, II and variant forms. The sialyloligosaccharide 2 was first demonstrated in human urine.