Recently several cases of lymphocytic bronchiolitis have been identified in workers at a nylon flocking plant. The objective of this investigation was to characterize the acute pulmonary reaction to exposure to airborne thoracic/respirable dust collected from this factory and to identify a component of the dust which may cause interstitial lung disease. Rats were intratracheally instilled with 2.5 mg of dust and pulmonary reactions monitored 1 day post-exposure. The acute reactions included: increased breathing rate, PMN infiltration, activation of macrophages, and an elevation of the albumin levels of the lavage fluid. These acute reactions dissipated at 29 days post-exposure. They were not associated with endotoxin or other water extractable components but were related to nylon shreds which were small enough to reach the alveolar region of the lung. The data indicate that nylon shreds can be generated during cutting of large nylon fibers and that this material can enter the lungs and result in inflammation and possible disease.