This paper concerns the interaction between hyaluronan and fibrinogen as model for protein-polysaccharide interaction. From rheological investigation, it is shown that a 3D physical network is promoted by mixing the two components; the mechanism is attributed to electrostatic interactions. The influences of the molecular weight and of the hyaluronan concentration are examined; the loose interaction obtained for addition of small amount of soluble protein induces a non-Newtonian behaviour which may be in direct relation with the behaviour observed previously on synovial fluids.