[en] Cancer is one of the leading causes of death worldwide. Efforts to overcome cancer is done by means of diagnosis and therapy. Nuclear medicine techniques using iodine-131 (¹³¹I) radioisotope is one of techniques that can be used in diagnosis and treatment some types of cancer, especially cancer of endocrine. Diagnosis and therapy using ¹³¹I radioisotope has been used in several hospitals in Indonesia, but the supply of ¹³¹I is currently hampered. Center For Applied Nuclear Science and Technology - National Nuclear Energy Agency has the ability to process ¹³¹I radioisotope using wet distillation method. To increase the yield and improve the safety aspects of the process, there should be a study to develop process technologies of ¹³¹I radioisotope. One of methods that can be applied to process technology is the separation method using an ion exchange resin column. In studies using columns, tellurium irradiated targets were dissolved along with ¹³¹I formed, tellurium and ¹³¹I were separated using a column containing ion exchange resin. The optimum condition of research were obtained using 2 N NaOH solvent, the resin type of Dowex 1x8 (Cl- form), 100 - 200 mesh and eluent of NH₄NO₃ 0.5 N. The characteristics of the final product that meets the standard reference of nuclear medicine, the separation process were obtained with the yield more than 70 %, radionuclide purity > 99 %, radiochemical purity > 95 %, the radioisotopes ¹³¹I in the form of a clear solution at pH 7.(author)