The structure of an extracellular polysaccharide (EPS) from Streptococcus thermophilus THS has been determined. A combination of component analysis, methylation analysis and NMR spectroscopy shows that the polysaccharide is composed of pentasaccharide repeating units. Sequential information was obtained by two-dimensional H-1,H-1-NOESY and H-1,C-13-HMBC NMR experiments. NMR data indicate different mobility within the EPS with a stiffer backbone and a more flexible side-chain.