The use of polycyclic phenolic compounds which have up to 20 benzene rings per molecule and are obtainable by reacting a tetrahydrobenzoxazine I where R1 is a hydrocarbyl radical and R2, R3, R4 and R5 are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals with one or more of the same or different phenols II where R7, R8, R9 and R10 are each independently hydrogen atoms, hydroxyl groups or hydrocarbyl radicals, and/or with one or more of the same or different tetrahydrobenzoxazines I, with the proviso that at least one of the substituents has from 13 to 3000 carbon atoms and the remaining substituents, when they are hydrocarbyl radicals, have in each case from 1 to 20 carbon atoms as stabilizers for stabilizing inanimate organic material against the action of light, oxygen and heat.