A method of boron removal from saline water containing boron and magnesium or calcium salts including a multi-stage reverse-osmosis (RO) separation process and comprising the steps of a first stage RO separation at pH<8.2; a second stage RO separation over at least part of the first-stage permeate; a third stage RO separation over the second-stage brine. The method is characterized in that the second stage separation is carried at pH>9 and the brine concentration is limited to a degree preventing Mg(OH).sub.2 or CaCO.sub.3 scaling on RO membrane surfaces, the permeate constitutes product water, and the brine contains boron and magnesium or calcium ions; the third stage separation is carried at weak-acid pH, whereby the bulk of the magnesium or calcium ions are separated with the brine, while the bulk of the boron ions are retained in the permeate. The method further comprises a fourth stage of separation over the third-stage permeate, where the bulk of the boron ions is separated from the third-stage permeate, and the permeate of the fourth stage constitutes product water with low boron content.