An electrolytic process and apparatus are disclosed for regenerating separate bed ion exchange resins used to demineralize aqueous solutions, preferably softened water, without the use of additional chemicals. The cation exchanger is regenerated by applying a DC electric voltage between an anode and a cathode across the cation exchanger whereby hydrogen ions produced at the anode displace cations previously absorbed on the cation exchanger during the previous demineralization cycle. The displaced cations move towards the cathode under the influence of the electric voltage and there form a caustic solution with hydroxyl ions produced by the cathode. The cathodically generated caustic solution is then used to chemically regenerate the anion exchanger in a traditional manner. Two embodiments of the invention are disclosed, one of which is an intermittent system of demineralization and regeneration and the other is a continuously operating system.