Endotoxin was prepared from Enterobacter agglomerans. One preparation was a purified lipopolysaccharide (PE) the other endotoxin bound to cell walls (CE). Test persons were exposed to 10-30 µg of these preparations. After exposure to PE, the FEV(1) as measured after four hours was decreased in a dose-related manner. CE caused a larger decrease than PE. DLCO was more decreased after exposure to PE. Fever occurred in the majority of subjects and several developed subjective symptoms of chest tightness.