The Hoesch synthesis consists in the condensation of a nitrile with a phenol, a polyhydric phenol, or a phenolic ether to form a hydroxyaryl or alkoxyaryl ketone. Usually, equimolar quantities of the reactants are dissolved in dry ether, preferably in the presence of a catalyst such as zinc chloride and dry hydrogen chloride is introduced. When phenols are used, imino ether hydrochlorides are sometimes formed as by-products and represent the only product of the reaction. The Hoesch synthesis has proved to be the most convenient synthetic method for certain polyhydroxyacylphenones and polyhydroxybenzophenones. Among these hydroxy ketones are anthelmintics, antidiarrhetics, and antiseptics. Extensions of the Hoesch synthesis are covered in this chapter.