The weathering process of stabilized (with three types of stabilizers and their mixture) polypropylene during long standing outdoor exposure and in the accelerated aging laboratory conditions was studied. The course of the aging process occurring in samples studied has been monitored by the structural changes of macromolecules (share of carbonyl groups on the basis of FT-IR) and polymer molecular weight (from GPC studies). The stabilizers used showed a synergism in light radiation protection of the polypropylene. The natural environment irradiation was more active in the aging process than the artificial one over the same irradiation dose.