SUNWARY Results of bench sc& studies of the elcctrodial~xis of saline water at tanpctaturcs in excess of 6O'C are summarized. The capacity. wilter content, resistance and burst strength of NcptonR AR1 Ii BZL IS3 anion selextivc membranes d d not show significant changes af~cr 100 da)s at 60' in 0.5N NaCI. Sodium form catian selective membrane NeptonR CR61 AZG 067 showed no dctectabk changes in appearance. resistancl? or ion exchange capacity after 7 days in w&r at 121 'C. Chloride form anion xlcctivs rwrnhrancs h'cptonR AR111 BZL 153 and AR111 EZG 067 under the same conditions had a capacity half-life of about 275O hours. Using an actibation energy of 17 kilocalories. caatculated from the decomposition of a commcrciai anion exchange resin. a hatf-life of ZOO,ooO hours for thermal dtxomposition is estimated for these membranes at 8o'C. It is concluded that the life-time in the field will be determined bv factors other than thermal decomposition. The t~xnpcmturc cocfficknt of rcsisrance of NcptonR membnncs is somewhat greater than 1 per cent per d~z Fahrenheit. With one exception. the transport number of NcptonR membranes is inmriant with tempnature. The water transfa drrrrases by roughly 15 per cent on passing from room temperature to 1.50-F. again with one. but a different. exceplion. Potentials at kast as high as 3 volts per 41 pair #JI be applied at 18o'F without polarization_ The pumping energy is substantially reduced and it is possible to accomplish a dcgrcc of dcmineraliution in one stage which would take two or more stages at 80-F a1 the same potential and linear &City. The cost of dcmincralizing sea water at 1BO'F is estimated for an 899 liters per second state-ofthe-art facility including a upti\c electric generator. The inwstmcnt is about Slt.5 million, including the generator. and total water costs are about 40 tints per thousand gallons which compares quite favorably with projections for very much larger dual-purpose distillation plants. The economics 0f producing 2 mgpd of 500 ppm mater from a 5O'F. . WH ppm feed are estimated for various operating tempet;tturu. With fuel at 30 cents per million Btu, a I5 per ant sasing is estimated for operation at IOO'F as compared to SO'F and a 25 percent saving at ISO". With free waste heat the cost savings are about 25 and 35 per cent respeztivety.