The solubility of water in molten mixtures of lithium chloride and potassium chloride containing 50.0, 53.0, 60.0, and 68.6 mole per cent lithium chloride was determined at 480 and 390oC in the pressure range zero to 26 mm. Melts were dried by alternate hydrogen chloride flushing and evacuation, and the solubility was determined by measuring the quantity of water vapor absorbed by the melt.