Subjects with no previous occupational exposure history to organic dust were exposed to an aerosol of endotoxin in form of lipopolysaccharide attached to cell walls of Enterobacter agglomerans. Lung function and airway hyperreactivity were measured before and at 4 and 24 hours after exposure. Levels of endotoxin equivalent to those found in textile mills caused a decrease in FEV(1) similar in size to that found in cardroom workers. Carbon monoxide diffusion also decreased. The exposure induced a decreased threshold for methacholine provocation in half of the subjects. There was no intercorrelation between the three parameters measured.