During the 9 years that separated the second edition of this textbook from its predecessor, our understanding of lung biology expanded vastly. The established approaches to occupational lung disease have traditionally involved careful use of epidemiologic methods, performance of pulmonary function testing on selected populations at risk, and quantitative sampling for noxious inhalants at home or in the workplace. These approaches still form the mainstay of etiologic survey, but in keeping with contemporary knowledge, the causative mechanisms of lung diseases are now sought at cellular and molecular levels. Material added to this new edition provides a succinct background for interpretation of changes of this kind. Because interstitial inflammatory and fibrotic reactions are the subject of active research in many nonoccupational lung diseases, the information is widely applicable and is a strong indication of the current sophistication and diversity of industrial pulmonary medicine. The additions provided, together with a new chapter on protective respirators, are well done and enhance a text of already established worth.