The present invention relates to iodinated resins. It relates in particular to a process for preparing a polyiodide-resin wherein an anion exchange resin is contacted with a material capable of donating a member absorbable by the resin so as to convert the resin to the polyiodide-resin. `The absorbable member is selected from the group consisting of I.sub.2 and polyiodide ion having a valence of -1. In the process, conversion of the anion exchange resin to the polyiodide-resin is effected at elevated temperate and/or elevated pressure, the elevated temperature being about 100.degree. C. or higher, the elevated pressure being greater than atmospheric pressure. The present invention also relates to a substance comprising an iodine (impregnated) resin as produced by the above process.