At the Molecular Immunology Center, was designed a mutant of the interleukin-2 molecule without interaction with the alpha chain of the IL-2 receptor. This new mutant shows higher antitumor activity and less toxicity than human IL-2, that´s why it is a better candidate for human cancer therapy. The mutein synthetic gene was cloned into the pET28a expression vector and protein is produced in the E. coli BL-21 (DE3) strain fused to a six histidine sequence at N terminal. Similar to other experiences the IL-2 mutein is produced as inclusion bodies. For recovering a fully active protein a purification procedure including in vitro refolding steps is needed. The current mutein purification process involves a solubilization step with SDS detergent followed by an Immobilized metal affinity chromatography in order to remove contaminant proteins. After that, endotoxin is removed using Fase reverse chromatography. Finally, the protein is turn to the formulation buffer using Size Exclusion Chromatography with G-25 Sephadex matrix. In order to improve the quality of the resultant protein, we modified some of the purification steps and conditions. The increase of SDS content and the addition of a reduction stage with DTT were evaluated during the solubilization phase and the size exclusion chromatography was changed by ultrafiltration/diafiltration, in order to eliminate the organic solvent and to help with the final refolding of the protein. The proposed purification process allowed obtaining a consistent purified product, with similar physical-chemical properties to the product purified with the current process and higher quality.