Lavendomycin (1), a novel hexapeptide antibiotic with potent antibacterial activity, was recently isolated from Streptomyces lavendulae subsp. sp. On the basis of chemical and spectroscopic evidence (including acid hydrolysis, Edman degradation, mass spectrometry, NMR spectroscopy, etc.), the structure of lavendomycin (C₂₉H₅₀N₁₀O₈) was elucidated. It is a hexapeptide containing a new amino acid, L-3-methylarginine (3-MeArg). The amino acid sequence was unequivocally determined as 3-MeArg-Dab-Pip-Pro-AAbu-Ser. The absolute configuration of lavendomycin was established except for the configuration at C-3 of the 3-methylarginine residue.