Abstract: The present invention relates to a process for the immobilization of ion exchange resins originating from radioactive produce (waste) reprocessing plants, the said resins being immobilized in a cement, preferably of the CLK type, wherein, before immobilization in the said cement, the said resins are treated with an aqueous solution containing NO.sub.3.sup.- and Na.sup.+ ions, the quantity of NO.sub.3.sup.- ions in the said aqueous solution being calculated so as to ensure that all the sites in the resins are saturated, assuming that all the resins treated are of anionic type and that the quantity of Na.sup.+ ions used in the said aqueous solution, or added in a second step, ensures on the one hand that the medium has a basic pH and on the other hand that all the sites in the cationic resins are saturated.