The alkylation of biphenyl with t-butylalcohol (TBA) over HY and ultrastable Y zeolites produced by multistep temperature programmed (MSTP) steaming procedure is studied in a stirred batch reactor using cyclohexane as solvent. 4-t-Butylbiphenyl (4-TBB) was observed as the major product with all the HY zeolites studied. However, the selectivity to 4,4'-di-t-butylbiphenyl (4,4'-DTBB) increased with framework dealumination and latter it decreases with the severity of dealumination temperature. The various reaction parameters affecting the activity and selectivity of the products such as temperature, catalyst amount, molar ratio and reaction time were investigated. The isomerization of 4,4'-DTBB over steam-treated HY zeolites is also discussed. (C) 2004 Elsevier B.V. All rights reserved.