Cumene dealkylation activity was determined for a series of dealuminated zeolites which were prepared by treatments with EDTA, SiCl₄, and steam at elevated temperatures. Upon dealumination the catalytic activity increased progressively up to 50% of framework aluminum removal. This is related to the increase of acid strength after aluminum removal and the extraction of weak acid site. However, beyond Si/Ai ratio close to 6, the acid strength of zeolite do not vary and the TOF based on framework aluminum is constant. Nonframework aluminum played a positive role in the enhanced catalytic activity. The variation of catalytic activity with cation was also examined. Catalytic activity is greatest for the small polyvalent cations. Comparison of the hydroxyl group with catalytic activity shows that the active sites are the acidic hydroxyl groups.