Recent studies on catalysis by heteropoly acids (HPA) for the Friedel-Crafts acylation of arenes and related Fries rearrangement of aryl esters are reviewed. It is demonstrated that HPA-based solid acids are efficient and environmentally friendly catalysts for these reactions, usually superior in activity to the conventional acid catalysts such as H2SO4 or zeolites. (C) 2003 Elsevier B.V. All rights reserved.