The effect of inhalation exposure of various biological agents associated with organic dusts on the function of guinea pigs pulmonary phagocytes was investigated. Agents included antigens of Erwinia herbicola, Thermoactinomyces vulgaris, and Aspergillus fumigatus; endotoxin of Erwinia herbicola; bacterial protease; and a fungal glucan preparation. Pulmonary parameters monitored in this study were cellular differential counts from bronchoalveolar lavage, and superoxide anion and or hydrogen peroxide production by phagocytic cells. Most of the agents caused an influx of neutrophils, lymphocytes, and red blood cells to the lung, and an enhancement of secretion of reactive oxygen species by pulmonary phagocytes. However, the relative magnitude of the inflammatory response varied greatly among these biological agents. In general, antigens of Erwinia herbicola and Aspergillus fumigatus were most potent, while bacterial protease was least effective.