The methodology for the optimization of an electrolytic plant for the production of deuterium is described. The basis of the optimization is to minimize the amount of electricity used in the electrolytic process, and this is assumed to be proportional to the total amount of gas evolution from the plant. Because the plant consists of two sections, i.e., the feed cascade and the reflux cascade, the conditions where the amount of gas evolution in each cascade is minimum were developed separately. The no-entropy condition, where two feed streams fed to a stage must have the same composition, was used in the optimization of the reflux cascade. From the results of the optimization, it was found that the location of the feed inlet to the reflux cascade and the number of stages in the reflux cascade are the major parameters in the optimization and, also, that the number of stages in the feed cascade does not significantly affect the optimum gas evolution results.