Avilamycin is an antibiotic complex produced by cultures of the organism Streptomyces viridochromogenes, strain NRRL 2860. These compounds belong to the orthosomycin family of antibiotics. Structural composition of the major avilamycins and several minor avilamycins are known. Nine additional minor avilamycins, designated F through N, have been isolated via semi-preparative silica gel or reverse-phase high performance liquid chromatography with final purification using a reverse-phase column loading solvent switching technique. 1H NMR and mass spectroscopy, negative ion fast atom bombardment (neg FAB) and electron impact, were used to structurally identify the avilamycins. All of the compounds were microbiologically active and similar in structure to other known avilamycins. Using classical degradation studies1, 2) avilamycin was shown to be a member of the orthosomycin family of antibiotics, (flambamycin3) and the everninomicins4)). Structural characterization of avilamycins A, B and C was first reported by WRIGHT5), in an addendum, and later published by KELLER-SCHIERLEIN6.7). The structures of four additional avilamycins D" D2, E and A' have recently been reported (personal communication, A. P. RAUN, Eli Lilly and Company with Ciba-Geigy, March, 1981). All of the above avilamycins are derivatives of A with changes at the C-45 linkage and/or the C-56 ketone adduct. The purpose of this study was to determine the structure of several additional minor components present in analytical standards of avilamycin and extracts of the fermentation product. Several unique modifications of avilamycin were found.