Monoallyl guaiacol such as eugenol, o-eugenol and chavibetol are industrially important compounds, which were synthesized by the allylation of guaiacol using zeolite HY. The reaction was performed in an autoclave in the temperature range 140-200 degrees C and allyl alcohol to guaiacol mole ratio 1:4, under nitrogen pressure. Among zeolites, HY gave maximum guaiacol conversion (46%) compared to H-beta (28%), H-mordenite (15%) and HZSM-5 (4%) when compared under identical reaction conditions. Zeolites showed better selectivity (> 85%) for monoallyl guaiacol than K-10 montmorillonite clay (47%). The pore architecture and acidic sites of the zeolites seems to influence the product selectivity. (c) 2005 Elsevier B.V. All rights reserved.