A method for the combinatorial synthesis of oligosaccharides comprising the steps of: (i) conjugating a saccharide building block containing orthogonally protected functional groups to a solid support, the protection being via at least one protecting group, (ii) cleaving the or each protecting group from functional groups on the monosaccharide building block through which there will be no chain elongation and capping these functional groups with a capping moiety which comprises a protecting group or chain terminating moiety, and (iii) sequentially removing the protecting groups from the functional groups through which there is intended to be chain elongation and glycosylating with another orthogonally protected building block.