The aim of the editors of this volume is to use basic and ap­ plied studies in the field of mutagenesis to approach a problem of especial concern. The problem is that of the usage of toxic chemicals, particularly agricultural chemicals, in ever-increasing quantities in those parts of the world that feed the most people. Agri­ cultural chemicals that are in use in Pakistan are emphasized here. These are the same chemicals that are in use throughout the develop­ ing world, although the quantities of the different types that are used may vary from country to country, and from region to region within countries. A number of these chemicals can no longer be sold in Europe or in the United States, and it is often difficult to iden­ tify a scientific reason as to why they are sold at all. It is ironic that toxic chemicals are used as a humanitarian device to rid the world of Pestilence and Famine — two of the Horsemen of the Apocalypse. If we do not wish poisonous chemicals to become the fifth Horseman of the Apocalypse, then we must begin now to identify and regulate the large-scale usage of toxic substances everywhere.