Perchloric acid immobilized on silica gel has been found to be an efficient and expedient catalyst for geminal diacylation of aldehydes. A wide variety of aromatic and aliphatic aldehydes can be easily transformed into the corresponding acylals using 0.5 mol% HClO4-SiO2 Within 2-10 min under solvent-free conditions at room temperature. The notable advantages of this protocol are: the reaction requires less reaction time and only stoichiometric amount of acetic anhydride being used, is highly economic and the catalyst is recyclable. (c) 2006 Elsevier B.V. All rights reserved.