The chemical structure of an exopolysaccharide produced by Lactococcus lactis subsp. cremoris B40 is studied, explaining earlier reported analytical discrepancies. The EPS was found to have a molecular mass of 6.8x105gmol-1 and a molar ratio of rhamnose:galactose:glucose:phosphorus of 1:1.3:2:1.1. 31P NMR indicated that a single phosphate group is present as a phosphodiester. EPS B40 was chemically modified using 0.6M H2SO4, 28M HF or 2M NaOH. From these modifications it could be concluded that galactose 1-phosphate was linked at the 3-position of 1,2,3,4-linked galactose in the backbone of the EPS. Furthermore, it appeared that during the hydrolysis step of the sugar composition analysis the galactose 3-phosphate linkages were only partially split and that, as a result, the amount of galactose was underestimated in presence of phosphate. Finally, it was demonstrated that a crude cellulase preparation was able to degrade dephosphorylated and partially de-rhamnosylated EPS.