In the lactic acid bacterium Lactococcus lactis, a cell wall polysaccharide (CWPS) is the bacterial receptor of the majority of infecting bacteriophages. The diversity of CWPS structures between strains explains, at least partially, the narrow host range of lactococcal phages. In the present work, we studied the polysaccharide components of the cell wall of the prototype L. lactis subsp. lactis strain IL1403. We identified a rhamnose-rich complex polysaccharide, carrying a glycerophosphate substitution, as the major component. Its structure was analyzed by 2D NMR spectroscopy, methylation analysis and MALDI-TOF MS and shown to be distinctly different from currently known lactococcal CWPS structures. It contains a linear backbone of repeated α-L-Rha disaccharide subunits, which is irregularly substituted with a trisaccharide occasionally bearing a glycerophosphate group. A poly (glycerol phosphate) teichoic acid, another important carbohydrate component of the IL1403 cell wall, was also isolated and structurally characterized.