Airborne gram-negative bacterial endotoxin levels were quantified in a live chicken hanging (shackling) room of a poultry processing plant. The mean respirable dust levels at the entrance and exit of the shackling line were 1.13 +/- 0.12 and 0.72 +/- 0.06 mg/m3, respectively, or approximately 6% of the total dust. Endotoxins constituted 43.3 +/- 2.8 micrograms per gram of respirable dust. Airborne endotoxins were present in the total dust at the mean level of 918.4 +/- 159.0 ng/m3 at the room entrance and 634.0 +/- 96.9 ng/m3 at the exit, with respirable levels of 44.3 +/- 7.8 and 33.6 +/- 2.2 ng/m3. Inhalation of gram-negative bacterial endotoxins can result in respiratory and systemic pathophysiology. The potential for adverse health effects in the working environment of the live poultry processing industry is discussed. Medical studies of workers in this area are required to confirm or deny the existence of occupationally related health effects.