The presence of appreciable quantities of boron, both in drinking water and in that used for watering, deteriorates the quality of the water. Therefore, the WHO recommends in its Guides for the Quality of Drinking water, a value with a maximum of 0.3 mg/L based on the NOEL (no-observed-adverse-effect-level). In the case of watering water, phytogenics effects may appear at levels of 3 mg/L. These levels of boron are due both to natural causes (present in silts) and those of human origin (present in detergents and soaps). The rejection of boron in systems of reverse osmosis is low under normal conditions of operation, between 40-60%. The rejection of boron depends mainly on the recovery and the pH of the feed water to the system, In this study the effect of these parameters on brackish water, previously subjected to a desalination stage, is analyzed. The results show an increase in the rejection of boron at pH values of 9.5 and above. Increasing the work pressure also increases the rejection of boron.