Quinones, which may be generated from lignin and lignin-related materials, and their Diels-Alder derivatives were evaluated as delignification promoters. Compared to anthraquinone at a 0.1% addition level, benzoquinones and oxidized lignin showed little or no effect. However, some naphthoquinones were found effective at higher addition levels, and a mixture of dimethyl-anthraquinone isomers was found to be superior to anthraquinone. The substituted anthraquinones, phenanthrenequinones, and fully aromatized naphthoquinones appear to function in a reduction/oxidation cycle such as that proposed for anthraquinone.