Packing cases used for the transport of art objects must provide complete and self-contained protection from the external environment, often for long periods of time. The demands placed on the physical properties of the materials used in the fabrication of packing cases are immense. Because of this, other considerations may be overlooked. One such factor is damage caused by the chemical instability of many of the materials that are used. Such damage is a major problem in display and storage cases within the museum. The release of acids, oxidants, solvents, plasticizers, and other additives and degradation products by display and storage materials causes considerable damage which often is not readily apparent. This paper discusses approaches to dealing with this problem in packing cases. Lists of suitable and unsuitable materials, methods of evaluating new or unknown materials, and ways of minimizing damage from the unavoidable use of unsuitable materials are covered.