Mechanical degradation of polymer solutions is an important problem which has to be assessed before injection into a reservoir. The main consequence is a viscosity loss due to macromolecules breakage which can strongly reduce the polymer solution effectiveness in controlling the water mobility inside the reservoir. Flow experiments have been performed by recirculating hydrolyzed polyacrylamide solutions through a small pack of sand particles. Polymer characteristics determined by viscometric and light scattering measurements have been analysed before and after injection at various flow rates. A normalized rate of degradation was defined by comparing the initial and final values of the intrinsic viscosity of solutions. The parameters investigated were: polymer concentration, molecular weight, concentration and nature of electrolytes.