Phosphorylated alkylated phenol/phenol ester mixtures in which the weight ratio of the alkyl moiety to the phenol moiety ranges from 0.05 to about 0.63, and the number of carbon atoms per alkyl moiety ranges from 3 to 16, preferably from 3 to 12, which mixtures have satisfactory viscosity range and impart to polymeric materials and especially to polyvinylchloride plasticized therewith good light and heat stability: a process for producing such phosphorylated alkylated phenol/phenol ester mixtures; and polymeric materials plasticized therewith.