Discusses the causes of fading against the background of the present knowledge of fundamental photochemistry and estimates the value of methods which have been recommended for protection against the action of light. Describes four types of photochemical processes which may lead to fading and gives examples of these processes. Considers the main external factors which influence the rates of fading; the humidity of the atmosphere, the spectral distribution of the radiation to which samples are exposed, and the temperature. Mentions external factors which influence the fading of colored materials and which are inherent in the systems. These include; the constitutions and properties of the dyes, the constitutions and properties of the materials to which the coloring matter has been applied, the physical state in which the dye is present, and the properties of other substances present in the system. Recommends excluding those wave lengths in interior illumination which do not affect viewing, lowering the humidity to improve the light-fastness of most dyeings, keeping samples in a dust-free atmosphere to prevent foreign substances reacting unfavorably on the light-fastness, and investigating further possibilities for the prevention of photo-destruction of dyestuffs on fundamental grounds. -- AATA