The adsorption of an organic high molecular polyphosphonate on bovine enamel and synthetic hydroxyapatite has been studied. Concentration and particle size of the solids and also pH and concentration of the phosphonate solution are important parameters for the amount of adsorbed polyphosphonate. During adsorption of the polyphosphonate, phosphate ions are released in solution. This observation correlates with the results of adsorption experiments in which low molecular diphosphonates were used. Adsorption kinetics seem to obey Langmuirs equation. The affinity constants and the binding capacities are calculated.