Increasingly it is realised that exposures to organic dusts are harmful to respiratory health. Endotoxins are a common contaminant of such dusts and are recognised as possible aetiological agents in respiratory disease in exposed individuals with such occupations. Exposures in different working environments and occupations have been measured by different investigators. Comparisons, however, are invalid due to the use of differing sampling, extraction and assay techniques. This paper presents data drawn from a study of 9 different industries comparing endotoxin exposures. Endotoxin exposures are presented as both environmental levels (per unit sampled air) and by contamination within the dust sampled (per mg of dust collected).