Anti-aluminium monoclonal antibodies (mAbs) were prepared using aluminium chloride-bovine serum albumin complex (Al-BSA) as immunogen. Competitive enzyme-linked immunosorbant assay (ELISA), using an Al-BSA coated immunoplate, demonstrated that mice immune sera showed stronger reactivity to AlCl3 than to BSA. Supernatants from hybridomas prepared from cloned anti-Al antibody-producing cells reacted in ELISA assays whether the metal was bound to proteins like calmodulin (CaM) and S100b protein or to immunogen BSA. Moreover, addition of citrate, a potent ligand for trivalent cations, resulted in a significant withdrawal in mAb recognition of aluminium which was previously bound to either CaM or S100b proteins. The anti-Al mAbs also reacted with aluminosilicate complexes formed from aluminium chloride and silicic acid. The results indicate that the monoclonal antibodies recognized aluminium alone, aluminium bound to silicate, or aluminium bound to a protein core and thus may be used as an immunologic tool for identifying aluminium in both in vitro and in vivo systems.