The numbering of monobactams follows that of the IUPAC; the nitrogen atom is position 1, the carbonyl carbon is 2, the α-carbon is 3, and the β-carbon 4.
A numeración dos monolactams segue a da IUPAC; o átomo de nitróxeno corresponde coa posición 1, o carbono carbonilo é o 2, o carbono α é o 3, e o carbono β o 4.