Inhibitory activity of 14 phosphonic analogues of phenylglycine, substituted in aromatic ring by fluorine and chlorine, was determined towards porcine aminopeptidase N. The obtained data served as a basis for studying their interaction with the enzyme as modelled by the use of Schrödinger Release 2018 program. The observed linearity between modelled Gibbs free energy differences and inhibitory constants indicated the usefulness of this program. The obtained binding mode was compared with this modelled for bovine lens leucine aminopeptidase. Although both enzymes differ in the number of zinc ions present in the active site, they are considered to exhibit similar activity towards substrates and inhibitors. Our studies seem to support that supposition since the modes of binding of the studied inhibitors are quite similar. Additionally, inhibitory activity of the phosphonic analogues of phenylglycine towards barley aminopetpidase was determined showing that this enzyme could be considered as neutral aminopeptidase.