The biosynthesis, biological activity, and ecological significance of secondary metabolites (natural products) are examined in this book. All the major classes of secondary metabolites are considered, according to the basic 'building blocks' from which they are derived. Examples are given of compounds found in insects, plants, and microorganisms; and the pharmacological and toxicological properties are highlighted. In the final chapter, the possible ecological significance of secondary metabolites is explored, and this feature is of increasing interest to all those who study natural products For this second edition special mention has been made of the isolation and characterization of the enzymes of secondary metabolism; and of the new NMR techniques which have revolutionized the elucidation of biosynthetic pathways.