Abstract: Disclosed is a process for stabilizing polyamides against the damage effected by light, heat and/or oxidation while improving the differential dyeability, and processing stability therefore, comprising incorporating therein by melt-processing a synergistic additive system resulting in a uniform and intimate mixture with said polyamide, said additive system is selected from the group consisting of (I), (II) and (III)(I) is from 0.01% to 1% by weight of a sterically hindered phenylphosphonite (Ia) with from 0.05% to 5% by weight of oxanilide (Ib) or said (Ia) together with from 0.05% to 5% by weight of an aromatic di- or tri-carbonyl compound containing at least one, and preferably two hindered amine moieties (Ic);(II) is from 0.05% to 5% by weight of oxanilide (IIa) together with from 0.05% to 5% by weight of a aromatic di- or tri-carbonyl compound (IIb) containing at least one hindered amine moieties;(III) is from 0.01% to 1% by weight of a sterically hindered phenyl phosphonite (Ia), from 0.