This program is designed to investigate the major causes of pulmonary cancer in man through lung cancer induction in animals. We are currently studying the carcinogenic potential of subfractions of air pollutants and cigarette smoke condensate polynuclear aromatic hydrocarbons with our system of wax-retaining pulmonary implants in rats. The histogenesis of the neoplasms so induced is also being studied employing EM techniques, primarily. Secondly, we are investigating the critical factors responsible for fiber carcinogenesis in the lung and pleura which depend on structural configuration of the particles of fibers such as the gypsums, metal whiskers, talcs, asbestoses, and fibrous glasses and a variety of other durable fibers. An effort to develop a workable hypothesis on the primary effect of the fiber on cells is in progress.