A method is described which is specific for the extraction of lipopolysaccharides from R form bacteria. The extraction mixture which is monophasic, consists of aqueous phenol, chloroform and petroleum ether. R form lipopolysaccharides (glycolipids). due to their lipophilic nature, are completely soluble in the mixture. S and T form lipopolysaccharides as well as proteins, nucleic acids, and polysaccharides, are insoluble, and they are excluded from the extracts. The method is mild, as it can be carried out at below 10°. The yields are generally higher than those obtained by phenol-water extraction, and the products are usually water-soluble. Lipopolysaccharides have been successfully extracted from all R form bacteria so far attempted.