Stabilizers for enhancing the resistance of synthetic resins to deterioration when exposed to elevated temperatures and/or ultraviolet light comprising from about 0.001 to about 10 parts by weight of a bisphenol phosphite having the formula ##STR1## wherein R.sub.1 is tertiary-butyl or tertiary-amyl, R.sub.2 is alkyl having from one to about nine carbon atoms, R.sub.3 is hydrogen or alkyl having from one to about four carbon atoms, and R.sub.4 is alkyl having from one to about thirty carbon atoms; and from about 0.001 to about 10 parts by weight of a phenol having the formula ##STR2## wherein R.sub.5 is alkyl having from one to about four carbon atoms; and stabilized synthetic resin compositions comprising such stabilizers.