The thermal stability of polyvinyl chloride (PVC) as one of the major manufacturing problems has been dealt with quite extensively for some decades. Apparently, there seems to be no remaining problem in processing PVC, because excellent stabilizers have been developed for use with it. However, there are still wide discrepancies among reported papers [1–14] on the mechanism of dehydrochlorination of PVC and the mechanism of stabilization by thermal stabilizers. The thermal decomposition of PVC is primarily a dehydrochlorination reaction [15], both in nitrogen and oxygen. However, it is a formidable task to summarize the reported results because of the difficulties associated with the characterization of prepared PVC. Therefore, improving the formulation from the economical and toxicological standpoint has been considered a real problem. Moreover, the explanation for the role of each additive in the field of processing has been done only through personal knowledge.