The increasing use of products from recycled polymers, or from blends with recycled polymers exposed to the outdoors, implies the need for good weathering resistance. This is particularly important when the recycled material comes, in turn, from products exposed during their lifetime to the sun. In this case the presence of C=O groups in the macromolecular chains strongly increases the photooxidative degradation kinetics of these secondary materials. In this work the change of the photooxidative degradation of blends of virgin and photooxidized polyethylene was evaluated as a function of the C=O content present in the material. As expected, the presence of the C=O groups strongly increases the photooxidation kinetics, as revealed by the increase of the carbonyl compounds, and by the decrease of the elongation at break. It was confirmed that the increase of C=O groups is dependent on the content of the same groups, whereas this is not true for the mechanical properties. The use of UV stabilizer strongly improves the weathering resistance of these materials, which become almost insensitive to the initial amount of C=O groups. (C) 2003 Wiley Periodicals, Inc.