An investigation was made of the reactions resulting from treatment of Kraft lignin and lignin model compounds with ozone. Ozonolysis of aromatic compounds usually results in ring opening and formation of carboxyl groups. While destruction of lignin chromophores occurs during oxidation, because of the specificity of the reaction of lignin with ozone, the conclusion is drawn that less damage occurs to the lignin macrostructure during ozonolysis than during oxygen bleaching processes. -- AATA