Friedel-Crafts sulfonylation of benzene and its derivatives was carried out using FeCl3-based ionic liquids. These liquids serve as an efficient media as well as Lewis acid catalyst, furnishing good yields of sulfones, under mild conditions. In pursuit of development of a catalytic system, we have studied the use of these ionic liquids, in catalytic amounts for a range of substrates, under conventional conditions. The use of these liquids as an aid for microwave heating and as effective catalysts for sulfonylation was also studied. (C) 2004 Elsevier B.V. All rights reserved.