A preliminary communication from our group assigned a tentative structural formula for amicetin. After a more detailed study, made possible especially by the availability of a larger quantity of the antibiotic, this structure assignment has been revised and evidence is presented in this paper that amicetin is better represented as I. Methanolysis of amicetin (I) yielded, besides cytimidine (II), the methyl glycosides (VI) of a neutral sugar, amicetose (VII), and of an amino sugar, amosamine (IX). Periodate fission of the 2,4-dinitrophenylhydrazone of amicetose (VIII) gave acetaldehyde and a derivative of succindialdehyde, leading to structure VII for the neutral sugar. Various degradations of amosamine and its derivatives were conducted and the results showed the amino sugar to be IX. Evidence is presented for the mode of linkage of amosamine, amicetose, and cytimidine in amicetin shown in structure I.