Three large-pore zeolites (H-MOR, H-Y and H-BEA) were studied as catalysts in the liquid-phase tert-butylation of toluene by tert-butanol. The catalytic activity and para-selectivity of zeolite catalysts and the main secondary reactions (isomerization of 4-tert-butyltoluene and its dealkylation) are discussed. The most active zeolite catalysts for the studied reaction were H-MOR (17.5) and H-BEA (12.5) zeolites. The most para-selective were mordenite zeolites with maximum selectivity to desired 4-tert-butyl toluene near 90%, which was supported by molecular modelling. Tert-butylation of toluene over zeolite catalysts can be an ecofriendly process for obtaining 4-tert-butyltoluene which is intermediate product for fine chemicals. (C) 2003 Elsevier B.V. All rights reserved.