This paper summarizes the types of stains produced by the 1966 floodwaters on books in the Biblioteca Nazionale and the measures used to remove them. Six types of stains were encountered: incrustations from the mud; stains of microbial origin; gas, oil, etc.; stains from the original water-soluble size; stains from colored objects left in books (e.g., bookmarks); stains due to the leather bindings on the books. The last type was considered the most deleterious. Stain removal for the combined catalog of stains involved dry cleaning to remove incrustations, washing in water, rinsing in oxalic acid solution, and bleaching (sodium hypochlorite). The techniques for taking out the various types of stains are discussed briefly.