Chemically modified celluloses are used in the manufacture of rayon fiber, cellulosic films and plastics, mucilages and many other products. Deterioration of cellulosic materials can be caused by the technological processes associated with the isolation and purification of the cellulose, and impurities either natural or introduced during handling and storage. The nature of these changes, their influence on cellulosic materials and ways of limiting their effects, especially for paper products and cellulosic based film material, are discussed.