A structure of the O-polysaccharide (O-antigen) of Escherichia coli 0158 has been reported (Datta, A. K.; Basu, S.; Roy, N. Carbohydr. Res. 1999, 322, 219-227). In this work, we reinvestigated the 0158 polysaccharide using sugar analyses, Smith degradation, and (1)H and (13)C NMR spectroscopy and established the following structure, which is at variance with the structure established earlier: alpha-L-Rhap3,4Ac 1 down arrow 3 -> 4)-beta-D-ManpNAc-(1 -> 4)-alpha-D-GalpA-(1 -> 3)-beta-D-GlcpNAc-(1 -> 6 up arrow 1 beta-D-Glcp This structure is in agreement with the predicted functions of genes found in the O-antigen gene cluster of E. coli 0158. (C) 2011 Published by Elsevier Ltd.