The present invention relates to the N-phosphonomethyl substituted tetrazole derivatives of formula I ##STR1## and tautomers thereof wherein R.sub.1 is aryl or biaryl; n is zero, 1 or 2 pharmaceutically acceptable mono- or di-ester derivatives thereof in which one or both of the acidic hydroxy groups of the phosphono functional group are esterified in form of a pharmaceutically acceptable mono- or di-ester; and pharmaceutically acceptable salts thereof; pharmaceutical compositions comprising said compounds; methods for preparation of said compounds and for the preparation of intermediates; and methods of treating disorders in mammals which are responsive to the inhibition of neutral endopeptidases by administration of said compounds to mammals in need of such treatment.