An O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide of Salmonella enterica O41, and the following structure of the O-unit was determined by chemical analyses along with 1D and 2D (1)H and (13)C NMR spectroscopy: -->2)-beta-d-Manp-(1-->4)-alpha-d-Glcp-(1-->3)-alpha-l-QuipNAc-(1-->3)-alpha-d-GlcpNAc-(1--> where QuiNAc stands for 2-acetamido-2,6-dideoxyglucose. The structure established is in agreement with the O-antigen gene cluster of S. enterica O41 and tentative assignment of the gene functions reported earlier.