A method is presented for the determination of trace quanities of phosphate in natural water which would be an improvement over the presently accepted spectrophotometric technique. The method involves cathodic stripping chronopotentiometry which was found to be an analytically sensitive technique. It is based upon the reversible oxidation of a metallic indicator electrode to an insoluble phosphate salt film. When copper is used as the indicator electrode, the detection limit is 10 ppb. The major drawback of the method is that under the electrolysis conditions employed, salt of mixed stoichiometry is deposited which subsequently results in two separate stripping steps. When mercury is the indicator electrode, the system approaches true Nernstian behavior. However, an observed interference of chloride ion has, to the present, limited application of the electrode to solutions containing phosphate in excess of 50 ppb.