An attempted summary of the state of knowledge concerning the conservation bleaching of old paper. The author perceives bleaching as a sui generis compromise between a wish to improve the aesthetic appearance of an object and the necessity of avoiding unfavourable changes, and places emphasis on the latter. Bleaching with the application of oxidation measures not only eliminates undesirable spots or lightens the entire leaf, but also produces numerous visible and invisible changes, always highly unfavourable for the given object. In turn, the usage of reducing agents avoids such alterations, but achieves only a slight bleaching effect. The article discusses in detail the employment of chloramine T and unambiguously oxidising agents: hypochlorites, hydrogen peroxide, and potassium permanganate, used by conservation workshops. The author presents proof of the greater harmfulness of the latter three agents in comparison with chloramine T. Alongside oxidation bleaching, the article considers also borohydrides as reducing agents. Their greatest conservation merit lies in the fact that they are capable of reverting, within certain limits, changes caused in the paper by natural aging as well as those generated by chloramine T. The lightening of the base obtained in this manner is, however, inconsiderable.