Why are books written? Since I have read many works by my colleagues with admiration, this question has always intrigued me. Further, writing a book takes a good deal of time and effort, and I had imagined that I would never undertake such a demanding task. A few unexpected events and circumstances have changed my mind. The first was the pleasant experience of editing Environmental Toxicology of Pesticides with Drs. Mallory Boush and Tomomasa Misato. This fine symposium volume occasioned many interesting responses, including a suggestion to prepare a more complete treatise on the grounds that such "proceedings" volumes, by their very nature, do not satisfactorily offer a complete and coherent description of the field, but cater chiefly to specialists. I myself prefer single-authored books for basic understanding of a scientific field. The second circumstance leading to the present volume was the avail ability of teaching notes from my course on the toxicology of insecticides. As the need to cultivate environmental awareness has increased, there has been a parallel increase in the enrolments of such courses both here and in other major institutions. Yet no comprehensive and up-to-date text has been available. The third factor which facilitated the effort was an especially pleasant sabbatical in Hawaii, where the availability of the excellent Hamilton Library at the University of Hawaii considerably eased my task.