In 1978, the OSHA cotton dust standard specified the use of the vertical elutriator (VE) for measuring airborne respirable dust. Efforts to define the etiology of byssinosis resulted in the analysis of VE dust filters for endotoxin. This effort has served as the basis for developing methods to evaluate different environments for endotoxin. The basic procedure consists of collection of a airborne gravimetric sample which is extracted with a pyrogen-free diluent and assayed by the LAL. However, there are no established guidelines for the sampling and analysis of aerosols or bulk samples for environmental endotoxin. This report reviews the methods that have been used to evaluate environmental endotoxin and makes recommendations regarding sample collection, storage, and analysis.