Over a number of years our laboratory has prepared several batches of lipopolysaccharides from Microorganisms (usually Enterobacter agglomerans or Pseudornonas syringae) isolated from cotton or cotton dusts. These preparations vary in activity in a muse model and when tested by the limulus amoebocyte lysate test. Although the methods used are the same, the amount of lipopolysaccharide obtained also varies. Pure (1 gm LPS/1 gm product) lipopolysaccharide by limulus testing from our UNC-CH laboratory was compared with two preparations of lipopolysaccharide (prepared by Difco Laboratories and Abbott Laboratories) obtained by Cotton Incorporated for research studies.