There is now abundant evidence that bacterial endotoxin is related to symptoms and diseases caused by organic dusts. Endotoxin is present in almost all kinds of organic dusts and airborne levels range up to several micrograms /m³. Experimental studies demonstrate that the effects induced by organic dusts are not related to the dust level. There is thus a need for guidelines on the amount of airborne endotoxin. The Committee on organic dusts of the ICOH has completed work on an endotoxin criteria document. The information assembled in the document demonstrates that endotoxin causes several disease entities in terms of toxic pneumonitis, airways inflammation and possibly chronic bronchitis. The suggested guidelines for toxic pneumonitis is 200 ng/m³ and for airways inflammation 10 ng/m³.