Bottromycin A, is hydrolyzed to tetrapeptide and dipeptide by alkaline hydrolysis. The structures of both peptides are determined to be 3,3-dimethyl-2-aminobutylylvalyl-3-methylprolylglycine and 3-methyl-3-phenylalanyl-3-(2-thiazolyl)-β-alanine. Hydrochloric acid hydrolysis of bottromycin A₂ gives A¹-isocaproyltetrapeptide and the structure is discussed on the bases of pKa studies. The structure of bottromycin A₂ is proposed from the results above described.