The paper contains a short review on the impact of in situ C-13 and H-1 MAS NMR to the elucidation of the mechanisms of alkylaromatics transformation over zeolite catalysts. The studies of deuterated benzene and cumene transformations over protonic forms of zeolites are considered to account for the mechanisms of H/D exchange in the aromatic ring and alkyl chain. The investigations of C-13 label transfer in the course of the rearrangements of specifically labeled benzene, cumene, n-propylbenzene and ethylbenzene are reviewed to provide deeper insight in the mechanisms of transalkylation, disproportionation, skeletal and nonskeletal rearrangements of alkyl chain, fragmentation and dealkylation/alkylation over zeolites. The main factors controlling selectivity of zeolite catalysts in alkylbenzenes transformations are established. (c) 2005 Elsevier B.V. All rights reserved.