Novel aminoglycosides of the following formula ##STR1## wherein R.sub.1 and R.sub.2 are identical or different and each represents a hydrogen atom or a methyl group, R.sub.3 represents a hydrogen atom or an optionally substituted aminoacyl group having 2 to 4 carbon atoms in the acyl moiety, and when all of R.sub.1, R.sub.2 and R.sub.3 are hydrogen atoms, the methylamino group at the 4-position is not oriented trans to the hydroxyl groups at the 3- and 5-positions; and acid addition salts thereof, which are useful as antibiotics; and process for producing compounds containing the same.