Nine ion-exchange resins were used to remove NH4 ions from aq. soins. of NH4ReO4 and to prep. the soins. for recovering HReO4 by vacuum evapn. at 60 degrees C under laboratory and pilot plant conditions. Breakthrough curves were used for the preliminary selection of the resins. The process was carried out in the sequence: sorption - washing - regeneration - washing. Two selected Amberjet 1600 and C 160 resins were studied for their ability to the regeneration by the treatment with aq. HCl, H2SO4, or HNO3 soins. The best results were achieved when 32% HNO3 soln. was used for the C 160 resin deb regeneration (counter-current). The content of impurities in the final soln. contg. 300 g Re/dm(3) was below 100 ppm.