This article describes, in narrative style, the research of the author and his associates, performed over a period of 30 years, that led to the identification and quantification of the anomalous structures in poly(vinyl chloride) (PVC) and to detailed descriptions of their mechanisms of formation. Also examined here are the implications of this work for the thermal stability of PVC, for the overall chemical mechanism of vinyl chloride polymerization, and for other relevant aspects of the chemistry and technology of vinyl chloride homopolymers and copolymers. (c) 2005 Wiley Periodicals, Inc.