Ever since the beginning of the plastics and rubber industry, it was realized that useful products could be produced only if cer- tain additives were incorporated into polymers. With the help of these additives, when physically dispersed in a polymer matrix, it has been possible to improve stability against thermal, oxidative, UV, hydrolytic and biological degradation, mechanical properties, flammability, cost, and processibility of plastics. The enormous growth of the volume of plastics consumed by modern society, and new application areas for plastics, have created a demand for new, better additives and better understanding of their functions in polymer systems. As a result of these trends there is a need for sharing of information on progress achieved in the area of polymer additives among engineers and scientists of the plastics industry and academia. This book is based on expanded and updated papers originally presented at the International Symposium on Polymer Additives, which was held in Las Vegas, Nevada, and was sponsored by the American Chemical Society, Division of Polymeric Materials Science and Engi- neering. The book is divided into five parts which cover advances in various areas of polymer additives. The first part is devoted to the progress in understanding of UV degradation and stabilization of various polymers. Oxidation degradation and stabilization of plastic materials is covered in the second part. New developments in the stabilization of PVC are presented in the third part.