The scientific and patent literature on polymerization of vinyl chloride (VCM) is very extensive. A comprehensive review covering the literature up to about 1984 was recently done by Felger (1986). Some less comprehensive but very useful monographs have also been published fairly recently (see Burgess, 1982, and Butters, 1982). The present account primarily deals with fundamental work on VCM polymerization. No attempts have been made to include in this report contributions which are solely reported in the patent literature. The report concentrates on those aspects of VCM polymerization where recent work has provided us with a better understanding or new insight. The progress in the field made during the last few years is mainly due to the fad that new or strongly improved experimental techniques (e.g., more powerful spectroscopic methods) have become available.