The structure of oxamicetin (C29H42N6O10), a new basic antibiotic produced by Arthrobacter oxamicetus sp. nov., was determined including its stereochemistry. Oxamicetin is closely related to amicetin, with 3-hydroxyamicetose (D-chromose C or olivose, i.e., 2,6-dideoxy-D-arabo-hexose) replacing amicetose in amicetin. Methanolysis of oxamicetin yielded cytimidine, methyl amosaminide, and compound III (identified as l-(β-3-hydroxyamicetosyl)cytosine). Alkaline hydrolysis gave compound V (hydroxycytosamine). Structural elucidation employed UV, IR, NMR, mass spectrometry, elemental analysis, mixture melting point determination, and the copper complex method for configurational assignment. The sugar moiety 3-hydroxyamicetose in oxamicetin is 2,6-dideoxy-D-arabo-hexose, which has been reported as a constituent of chromomycins and olivomycin (named D-chromose C or olivose). This study established the structure of oxamicetin, which differs from amicetin in its sugar component.