AbstractHigh specifie activity 32P‐Iabeled disodium ethane‐1‐hydroxy‐1,1‐diphosphonate has been prepared for specific use as a radiotherapeutic ameliorative treatment of osseous tumors by reacting 32P‐labeled phosphorus trichloride, acetic acid and water. This compound has been purified by crystallization of the disodium salt from a water‐ethanol solution. Product identity and purity were established by reverse isotope dilution analysis. Spectrochemical quantitation, thin layer chromatography, radionuclide beta energy and half‐life determinations are presented as essential procedures for establishing chemical and radiochemical purity when human distribution studies are planned.