||Zeolite NU-87 has both 10-MR and 12-MR apertures which are accessible only viathe 10-MR windows of the channels. Owing to this peculiar pore system, NU-87 mayoffer a unique reaction activity, selectivity and stability not found in other zeolites andserve as favorable catalyst for the disproportionation of aromatic compound withsomewhat bulky diphenylalkane intermediate. Disproportionation of1, 2, 4-Trimethylbenzene(TMB) to yield xylene and tetramethylbenzene(TeMB)is animportant process in the petrochemical industry because of the continuous demand forhigh-valued p-xylene and 1, 2, 4, 5-TeMB. Under this circumstance, zeolite NU-87 wassynthesized and applied to the disproportionation of 1, 2, 4-TMB. NU-87 was found tohave considerable catalytic potential for this reaction in terms of xylene yield andstability. These results were elucidated in view of pore structure and acid property ofNU-87.