Abstract: The present invention relates to 1-hydroxy-.omega.-(alkyl- or arylphosphinico)alkane-1,1-diphosphonic acids of the general formula I ##STR1## and to the salts of these acids of the general formula II ##STR2## where, in these formulae, R.sup.1 denotes an alkyl radical having 1 to 6 carbon atoms, a cycloalkyl radical having 5 to 7 carbon atoms or an aryl radical having 6 to 10 carbon atoms, R.sup.2 denotes a straight-chain or branched alkylene radical having 1 to 6 carbon atoms and A denotes a monovalent equivalent of a cation of an inorganic or organic base. In addition, processes are described for the preparation of these novel compounds.