Abstract: A process for the manufacture of ionic liquids by an anion exchange reaction of a quaternary ammonium, phosphonium, imidazolium, or pyridinium halide, providing the appropriate cation component, with an acid or a salt thereof, providing the appropriate anion component, involves carrying out said reaction under ultrasonication. Ionic liquids belong to a known class of chemical compounds and are useful as solvents for organic syntheses; they are of particular interest in view of their capability of replacing classical solvents and avoiding the toxicological and disposal problems associated with such latter solvents.