The ammonium salt of 12-tungstophosphoric acid was employed for the acetylation of a variety of alcohols, phenols and amines under solvent-free conditions at 30 C. This method showed preferential selectivity for the acetylation of the amino group in the presence of hydroxyl group. No, C-acylation was observed under the present conditions. The method is simple, mild and environmentally viable as it involves stoichiometric use of acetylating agent. The catalyst was found to be reusable for five cycles, without appreciable loss in activity.