<jats:p>The O‐specific polysaccharide of the 0114 antigen (lipopolysaccharide) of <jats:italic>Escherichia coli</jats:italic> 0114 and oligosaccharides obtained from it by Smith degradation and hydrogen fluoride solvolysis were analyzed, using proton and <jats:sup>13</jats:sup>C nuclear magnetic resonance spectroscopy and methylation. The results indicated that the 0114 polysaccharide has the tetrasaccharide repeating unit α‐<jats:italic>N</jats:italic>‐acetylglucosamine(1 → 4)β‐3,6‐dideoxy‐3‐(<jats:italic>N</jats:italic>‐acetyl‐L‐seryl)aminoglucose(1 → 3)β‐ribofuranose(1 → 4)galactose. In the polysaccharide the repeating units are joined through β1 → 3‐galactosyl linkages. This structure is compared with that of the serologically cross‐reacting <jats:italic>Shigella boydii</jats:italic> 08 antigen and the serological similarity is discussed.