The polymerization of N-vinylearbazole (NVC) by SK-500 molecular sieve obeys the relation, rate of polymerization (R) = [NVC]1,0(weight of SK-500)°−7Oat 30°C. Stirring increases the rate but the reaction order does not change. The highest catalytic activity, observed at 500°C precalculation temperature, does not correspond to the highest solid acidity of the sieve, realized at 200°C precalculation temperature. Pyridine and n-butylamine (⋍10−3M) inhibit and hydrogen chloride (⋍10−3M) and phosphoryl chloride (⋍10−4M) cocatalyze the polymerization. Both R and the degree of polymerization (F) increase up to a maximum at −9 −10% uptake of water (g/g of dry zeolite) and thereafter fall. Alumina and silica increase .Rp Pn decreases with an increasing alumina content and rises initially at low silica content, falling at a high concentration of the latter. Nitrobenzene retards the polymerization. P is independent of [NVC], percentage conversion, and weight of SK-500. It appears that the polymerization is initiated through Bronsted acid sites as well as through direct interaction of RE3+centers with a vinyl double bond of the monomer by a conventional cationic mechanism.