alpha-Fe2O3, gamma-Fe2O3 and Fe3O4 were prepared in the free form and also supported on montmorillonite K10 in situ. The resultant catalysts were activated at 120 degreesC (except for Fe3O4) and were used for the Friedel-Crafts benzylation of different arenes using benzyl chloride. The catalysts were characterised using FTIR and XRD. The reactions were carried out at different temperatures. Exceptional activity was found to be associated with K10-gamma-Fe2O3 the catalyst was reusable. K10-Fe3+ and FeCl3 impregnated K 10 were also prepared and activated at 550degreesC; their activities were compared with the above catalysts. All the forms of iron(III) oxyhydroxides and oxides were used for benzylation reaction using benzyl alcohol to study the decreasing in acidity on calcination of FeCl3-exchanged and impregnated K10. (C) 2003 Elsevier B.V. All rights reserved.