ECODAB (the E. coli O-antigen database) has been expanded to include information about glycosyltransferases (GTs) involved in the assembly of the O-antigen polysaccharide. Similarity searches have been performed to be able to determine GT functions that have not been reported prior to this work. In addition to suggesting the function of 179 GTs, the approach leads to the prediction of part of the O-antigen structures of a number of serogroups. The procedure suggests a novel way of combining genetic information with experimental techniques in structural analysis of oligo- and polysaccharides.