The present invention relates to a procedure for elimination of boron from sea-water by reverse osmosis membranes characterized in that it comprises: adding to sea-water a composition consisting of at least one metal together with at least one antiscaling-dispersant agent, and a second phase in which an alkalinizing agent is added until a pH of between 8-9.5 is achieved, which can furthermore consist of a third phase in which the fluoride content of the sea-water is increased following the second phase, or a third phase in which a high molecular weight alcohol is added to the water.