Abstract: Synthetic crystalline aluminosilicate zeolites are crystallized from an aqueous reaction mixture comprising sources of alkali metal oxide, silicate, aluminate and an ionene or ionomer which contains positively charged nitrogen atoms in such quantity as to satisfy some of the cationic sites of the eventual zeolite. The presence in the reaction mixture of such a polymer serves to direct crystallization of the zeolite, giving rise to the formation of large pore zeolites under conditions where small pore zeolites would otherwise result, to the formation of more siliceous zeolite than would otherwise result, and to the formation of certain species of zeolite essentially free of stacking faults, the crystallization of which has not heretofore been possible.