Nocardia kirovani cell walls possess a lipidic fraction, a lipolysaccharidic fraction and a peptidoglycan. The lipidic part is composed of glycerides, C(16) and C(18) free fatty acids, nocardic acids and of a carotenoid pigment. The lipopolysaccharidic part is composed of an arabinogalactan esterified by nocardic acids. The glycan strand consists of alternating 1-->4 linked N-acetylglucosamine and N-glycolylmuramic acid residues substituted by a peptide subunit in which the aminoacids Ala, Glu, meso-Dap are present in the molar proportions 1,7:1,2:1.