A description is given of a stabilizer composition comprising A) at least one nitrogen compound having a molecular weight of at least 150, selected from a secondary amine in which all substituents positioned α to the amine nitrogen atom are different than hydrogen, or, derived from the secondary amine, a tertiary amine, hydroxylamine, alkoxyamine or amide; and B) at least one iron compound. The stabilizer composition optionally comprises nitroxyl radicals. It is suitable for stabilizing nonliving organic material, especially polyolefins or homopolymers or copolymers of styrene, against the effects of light, heat or oxygen.