Aluminum ions (Al) and chromium (III) ions (Cr), as they exist in aqueous solution at neutral pH, adsorb onto calcium hydroxyapatite crystals (HAP) and severely inhibit their dissolution process, when present in concentrations less than 1 microM. Iron (III) ions (Fe), at concentrations up to 10 microM, have no effect on the dissolution process of HAP. The Fe-chelating agent desferrioxamine also forms strong complexes with Al but not with Cr. Desferrioxamine prevents the adsorption of Al to HAP and removes pre-adsorbed Al from the HAP surface, although not instantaneously, but has no significant effect on the adsorption of Cr to HAP. Desferrioxamine is also found to be capable of removing Al preadsorbed to bone powder.