Substituted hydroxylamine ester stabilizers corresponding to the formula ##STR1## wherein n is 0-2, X is a direct bond, --S-- or --CH.sub.2 S--, R.sub.1 and R.sub.2 are independently hydrogen, alkyl, cycloalkyl, aralkyl, R.sub.3 and R.sub.4 are independently alkyl, cycloalkyl or aralkyl, and R.sub.5 is hydrogen or the group ##STR2## are effective in stabilizing organic materials against oxidative, thermal and actinic degradation.