A heightened intensity of research in pulmonary toxicology in recent years has derived from several factors. One of the most compelling factors is the wide dissemination of environmental toxicants which produce pulmo nary effects or enter via the respiratory tract. The massive volumes of sci entific, technical, and lay literature are telling testimony to the general con cern about the effects of environmental contamination on the biosphere and specific concern about airborne toxicants and human health. Organic materials that are subject to volatilization and are rclevant to the respiratory tract have been reviewed among others, by Gerarde (1), and Fassett (2). Reviews on inorganic or radioactive materials appearing in the pharmacological literature (3, 4) give some recognition to the complexities of the respiratory route of entry. A review by Foreman (5) should be sin gled out as emphasizing the airborne inorganic materials. Despite the lapse of some years, these reviews provide a base for understanding much of what is known about important sources of occupational exposures to or ganic materials, metals, and minerals. The subject of air pollutants, despite a full measure of attention, warrants some treatment if only because of the immediacy of the societal problems to which they contribute. Selective fac ets of air pollutant exposures and effects have been singled out for discus sion as they have not received adequate coverage in the pharmacological literature and deserve special attention. Deposition and clearance of particles, the alveolar response, and early lung changes have been subjects for review. Selected sources of general in terest reflect a wide range of focus and format. One finds discourses on respirable air sampling such as that of Lippman (6), monographs on depo sition and retention of particulate material, e.g., Hatch & Gross (7), and specific reviews devoted to factors controlling deposition (8) and retention (9). Growing interest in mixtures of toxicants is manifest in numerous sym posia. Some have been devoted solely to early events in the lung following inhalation (10, 11) or to specific topics such as air pollution and lung bio-