AbstractThe primary structure of theEscherichia coliserotype K‐27 capsular polysaccharide has been investigated. The capsular polysaccharide was isolated fromEscherichia colistrain E56b, serotype 08:K27(A):H‐. Using methylation analysis, characterization of oligosaccharides obtained by partial acid hydrolysis and enzymic degradation, as well as1H nuclear magnetic resonance, the primary structure of the K‐27 glycan has been elucidated. The polymer was found to consist of tetrasaccharide repeating units of the following stru