Chlorophyll derivatives form a significant and growing element in the range of natural pigments used as food colorants. An account is provided of the methods of production and of the products formed under industrial conditions. Consideration is given to the formation of chlorophyll under biological conditions, together with a comprehensive summary of the structure and occurrence of all known natural chlorophylls. Brief details are provided of the function and natural environment of chlorophylls in biological systems, with information on their relative stability in vivo and in vitro, together with a description of the known major products of natural and artifical degradation. The economic value of chlorophyll derivatives is described, together with future prospects for exploitation.