A process for stabilizing an organic material, wherein the organic material is a thermoplastic polymer, against oxidative or thermal degradation, which comprises incorporating therein or applying thereto at least a compound of the formula I, wherein R 0 is or -CN, R 1 is -S-R 12, -SO-R 12, -SO 2 -R 12 or -CN; or R 1 and R 2 form together R 2 is hydrogen, -S-R 13, -SO-R 13, -SO 2 -R 13, unsubstituted or C 1 -C 4 alkyl substituted phenyl; hydroxy or C 1 -C 25 alkanoyl-oxy, R 3, R 4, R 5, R 6 and R 7 independently of each other is hydrogen, C 1 -C 25 alkyl, halogen, trifluormethyl, nitro, C 1 -C 25 alkoxy, C 7 -C 9 phenylalkyl, phenyl or or each pair of substituent R 3 and R 4 or R 4 and R 5 or R 5 and R 6 or R 6 and R 7, together with the linking carbon atoms, forms a benzene ring; and with the proviso that at least one of the radicals from the group of R 3 to R 7 is hydrogen; R 8 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 9 is hydrogen, alkali metal, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; C 3 -C 25 alkyl which is interrupted by oxygen or sulfur; benzhydryl or R 10 and R 11 independently of one another are hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; or R 10 and R 11, together with the nitrogen atom to which they are attached, form a 5-, 6- or 7-membered heterocyclic ring which is unsubstituted or is substituted by C 1 -C 4 alkyl or is interrupted by oxygen, sulfur or R 12 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 13 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 14 is C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 15 is C 1 -C 25 alkyl or C 7 -C 9 phenylalkyl, R 16 is halogen or nitro, R 17 is C 2 -C 18 alkylene, C 4 -C 18 alkylene which is interrupted by oxygen, sulfur or C 2 -C 18 alkenylene, C 2 -C 20 alkylidene, C 7 -C 20 phenylalkylidene, C 5 -C 8 cycloalkylene, C 7 -C 8 bi cycloalkylene, unsubstituted or C 1 -C 4 alkyl-substituted phenylene; R 18 is hydrogen, C 1 -C 8 alkyl or benzyl, R 19 is C 1 -C 25 alkyl or C 7 -C 9 phenylalkyl, and X is a direct bond, -SO- or -SO 2 -. R 0 is or -CN, R 1 is -S-R 12, -SO-R 12, -SO 2 -R 12 or -CN; or R 1 and R 2 form together R 2 is hydrogen, -S-R 13, -SO-R 13, -SO 2 -R 13, unsubstituted or C 1 -C 4 alkyl substituted phenyl; hydroxy or C 1 -C 25 alkanoyl-oxy, R 3, R 4, R 5, R 6 and R 7 independently of each other is hydrogen, C 1 -C 25 alkyl, halogen, trifluormethyl, nitro, C 1 -C 25 alkoxy, C 7 -C 9 phenylalkyl, phenyl or or each pair of substituent R 3 and R 4 or R 4 and R 5 or R 5 and R 6 or R 6 and R 7, together with the linking carbon atoms, forms a benzene ring; and with the proviso that at least one of the radicals from the group of R 3 to R 7 is hydrogen; R 8 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 9 is hydrogen, alkali metal, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; C 3 -C 25 alkyl which is interrupted by oxygen or sulfur; benzhydryl or R 10 and R 11 independently of one another are hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; or R 10 and R 11, together with the nitrogen atom to which they are attached, form a 5-, 6- or 7-membered heterocyclic ring which is unsubstituted or is substituted by C 1 -C 4 alkyl or is interrupted by oxygen, sulfur or R 12 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 13 is hydrogen, C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 14 is C 1 -C 25 alkyl, C 7 -C 9 phenylalkyl, unsubstituted or C 1 -C 4 alkyl-substituted phenyl; or unsubstituted or C 1 -C 4 alkyl-substituted C 5 -C 8 cycloalkyl; R 15 is C 1 -C 25 alkyl or C 7 -C 9 phenylalkyl, R 16 is halogen or nitro, R 17 is C 2 -C 18 alkylene, C 4 -C 18 alkylene which is interrupted by oxygen, sulfur or C 2 -C 18 alkenylene, C 2 -C 20 alkylidene, C 7 -C 20 phenylalkylidene, C 5 -C 8 cycloalkylene, C 7 -C 8 bi cycloalkylene, unsubstituted or C 1 -C 4 alkyl-substituted phenylene; R 18 is hydrogen, C 1 -C 8 alkyl or benzyl, R 19 is C 1 -C 25 alkyl or C 7 -C 9 phenylalkyl, and X is a direct bond, -SO- or -SO 2 -.