Hydroxyaminohydrocarbonphosphonic acid derivatives represented by the formula: ##STR1## wherein R.sup.1 is hydrogen or acyl,R.sup.2 is hydrogen, lower alkyl, ar(lower) alkyl or acyl, andA is lower alkylene, lower alkenylene or hydroxy(lower) alkylene, or the esters at the phosphono group thereof or the pharmaceutically acceptable salts thereof, excepting 3-(N-acetyl-N-hydroxyamino) propylphosphonic acid, 3-(N-acetyl-N-hydroxyamino)-2-hydroxypropylphosphonic acid, and their pharmaceutically acceptable salts, and processes for preparing the same.Included are compounds having antimicrobial activity against various pathogenic organisms.