The polymerization of large cyclic vinyl compounds is of considerable interest in the interpretation of the mechanism of action of complex organometallic catalysts. Numerous vinyl compounds have been investigated up to now but no study has been made of compounds containing large rings. Studies on the isotactic polymerization of vinylcarbazole have brought to light very important facts permitting of a number of inferences as to the mechanism of isotactic polymerization. Despite the large molecular volume of vinylcarbazole and the steric hindrances that should be expected due to this, a study of the polymerization kinetics has revealed reaction rates similar to those observed in the polymerization of other monomers. The study of the polymerization of vinylcarbazole and of other monomers showed that the butyllithium‐titanium chloride catalyst belongs to the class of organometallic complexes that act either by a stepwise or ionic mechanism. The specific features of complex organometallic catalysts in the polymerization of vinylcarbazole are evidently associated with preliminary activation of the active centers during which activation of the monomer also takes place. The formation of polymers with an isotactic microstructure is due to one of the possible mechanism of the catalysis, namely, to nonstepwise action. In the polymerization of vinylcarbazole in the presence of organolithium compounds and titanium tetrachloride the microstructure of the resultant polymer and the rate of polymerization depend upon the formation of other than primary complex compounds. The microstructure of isotactic polyvinylcarbazole shows a particular shape of spherulites, depending upon the nature of the catalyst.