A sensitive agarose-gel electrophoresis method has been developed for the visualization of lipopolysaccharide (LPS) samples from several Escherichia coli serotypes, such as 026:B6, 055:B5, 0128:B12, 0111:B4, 0127:B8, and K235. This method can detect as little as 0.5-6 microg of LPS depending on the serotype by treatment of the plates with toluidine blue, and it is able to measure sub-microgram amounts of samples, approx. 0.05-0.5 microg, when the staining with toluidine blue followed by Stains-All procedure is adopted. Treatment of LPS with alkali under anhydrous conditions removes the ester-linked fatty acids and the phosphate groups of the Lipid A component, producing the detoxified LPS. The carbohydrate neutral moiety obtained from the hydrolysate does not migrate during electrophoresis. This was utilized to monitor quantitatively the removal process of the Lipid A component for the formation of the detoxified LPS.