A review, with .apprx.35 refs. Compds. capable of forming chelate complexes with their PO double bond systems represent excellent host mols. for most of the biol. important classes of org. cations in polar media. Addnl. cooperative hydrogen bonds render even simple bisphosphonates highly selective: mono- and disaccharides, 1,2- and 1,3-amino alcs., arginine derivs. in peptidic environment and arom. guanidines can now be recognized with high efficiency and high selectivity. The Review Article presents this relatively new concept for mol. recognition which imitates in many cases the recognition motifs found in nature itself.