The acid-uptake and ion-exchange characteristics of wool oxidized with peracetic acid have been re-examined. It has been shown that oxidized wool is capable of ion exchange although the ion-exchange properties are similar to those of carboxylic acid cation-exchange resins and unlike those of sulphonic acid cationexchange resins. Oxidized wool was successfully converted to the ammonium "salt" and the ammonium ions exchanged with barium ions.