Aqueous solutions of 4-chlorophenol, 2,4-dichlorophenol, methoxybenzene, 1-naphthol, and naphthalene at a concentration of 0.5-1 × 10−4M reacted with two equivalents of ozone at pH 7.25-10.65 to form various oxidation products. When the reactions were conducted in the presence of nitrite ion (0.5-1.0 × 10−4M), a nitration reaction occurred with three of the five aromatic compounds (4-chlorophenol, 2,4-dichlorophenol, and 1-naphthol). Aromatic compounds that undergo nitration under the conditions of the experiments have a higher reaction rate than that for the reaction of ozone and nitrite ion.