The conservator's involvement in museum exhibitions is steadily increasing, particularly in the area of packing and transporting paintings. It is, therefore, important to consider carefully the various materials which are available for the construction of the outer case and the internal packing system. These materials must be evaluated in terms of their design capabilities, cost, and ability to reduce shock, vibration and environmental changes. This paper discusses the current types of packing cases and considers the various physical properties which must be controlled.