[en] ¹⁵³Sm-EDTMP has been widely used to palliate pain resulting from metastatic bone cancer. Its radiochemical purity is normally determined by ion exchange, paper chromatography and thin layer chromatography. Paper chromatography showed to be a rapid and reliable method, when used for the complex obtained in high ligand concentrations. However, when the complex was prepared in low ligand concentrations, the results presented significant differences from those obtained by ion exchange and thin layer chromatography. A comparative study on ¹⁵³Sm-EDTMP radiochemical purity determinations is presented, using these three methods to evaluate the complex obtained in high and low ligand concentrations. (author)