The existing methods of protecting cellulose from acid attack are reviewed. These methods are unsuitable to preserve paper and books or prohibitively expensive. The suggested new practice for deacidification consists of impregnating paper and books with a nonaqueous solution containing an organic solvent and a benign alkaline deacidification agent. Organic solvents are used because they wet paper more rapidly than water, have less swelling or distorting effect on paper, and are easier to dry from paper than water. The solution may be applied by immersion, spraying, or brushing. Laboratory aging studies made with single sheets of paper show that nonaqueous deacidification treatments can produce results equivalent or superior to present day aqueous treatments and increase the expected life of well-regarded, commercial, moderately acidic book papers from two to three times. Magnesium methoxide is selected as the preferred deacidification agent. Since 1968, solutions of 7% magnesium methoxide in methanol and trichlorotrifluoroethane or dichloromethane (1:3 parts) have been used to protect single sheet items. Whole books were deacidified by use of liquefied refrigerant gas solvents. The feasibility for treating library collections is described in terms of experimental results, probable costs, and conservation and industrial practices. -- AATA