Approximately ten years have elapsed since the second volume of the International Life Sciences Institute (ILSI) Monographs on Pathology of Laboratory Animals, Respiratory System, was first completed. New in formation of interest to pathologists has developed at a rather remark able pace during these years. Exceptional progress has been made in the routine identification of enzymes and cell products in respiratory cells. A better understanding has developed on the functions of cells of the respiratory tract and of the mechanisms involved in cell metabolism, particularly those involving toxins...