Methods have been elaborated for rapid location of biologically active bacterial endotoxin components on preparative thin-layer chromatography (tlc) by Limulus lysate clotting assay. The separation of the components from silicic acid is not necessary. Further assays were established for the semiquantitative estimation of endotoxic activites (Shwartzman reactivity, chick embryo lethality, and non-specific tumor resistance enhancement) without complete removal of silicic acid. Quantitative chemical analytical procedures were also elaborated to determine the molar ratios of the biologically active components separated and detected in the above tlc system. These included phosphorus, hexosamine, heptose, 2-keto-3-deoxyoctonate, and long-chain carboxylic acid content measurements. Here again, the chemical determinations were carried out in the presence of silicic acid.