Hygromycin, an antibiotic with a wide antibacterial spectrum, has been degraded to three principal units: 3,4-dihydroxy-a-methylcinnamic acid, an inosamine and 5-keto-6-deoxy-~-arabohexose. The hexose is attached by a glycosidic linkage at the 4-hydroxy position of the 3,4-dihydroxy-a-methylcinnamic acid. The inosamine is linked to the acid as a carboxamide.