PCT No. PCT/EP97/01865 Sec. 371 Date Dec. 30, 1998 Sec. 102(e) Date Dec. 30, 1998 PCT Filed Apr. 14, 1997 PCT Pub. No. WO97/39179 PCT Pub. Date Oct. 23, 1997A method of bleaching lignocellulosic fibers is disclosed which comprises the step of treating the lignocellulosic fibers with a bleaching composition comprising at least one oxidizing bleaching agent in aqueous solution in the presence of at least one additive which activates delignification or bleaching wherein the activating additive is a phenanthroline selected from the group consisting of 2,9-dimethyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline-disulfonic acid-disodium salt-hydrate, and 3,4,7,8-tetramethyl-1,10-phenanthroline.