Bandeiraea simplicifolia I (BS I) isolectins, immobilized on Sepharose beads, specifically retarded low molecular weight ligands containing terminal cu-o-galactopyranosyl and 2acetamido-2-deoxy-aD -galactopyranosyl residues. A BS I lectin-Sepharose column has been used to perform very efficient separations of structurally homologous sugar nucleotides and oligosaccharides. For example, UDP-glucose and UDP-galactose (and the corresponding 2-acetamido-2-deoxy derivatives) were separated by as much as three column volumes by a BS I lectin-Sepharose column. This column has also been used to resolve the alditols of lactose (P-o-Galp-(1 4 4)-D-Gk) and melibiose (a-o-Galp-(1 + 6)-~431~). to analyze the radiochemical purity of UDP-galactose and UDP-N-acetyl-D-galactosamine preparations, and to analyze the relative proportions of UDP-N-acetyl-D-glucosamine and UDP-N-acetyl-o-galactosamine in the UDP-N-acetyl-o-hexosamine pool isolated from cultured cells.