The liquid-liquid-solid equilibria in the two-liquid and two-liquid + one-solid quaternary regions for the quaternary system water + ethanol + l-butanol + potassium chloride at 25 degrees C have been determined. Distribution and selectivity curves are represented for this system, and they are compared with those previously obtained fur the water + ethanol + l-butanol + sodium chloride system at 25 degrees C; the different salt effects of both salts have been discussed. Tie-line and tie-triangle data have been correlated using a modification of the Eisen-Joffe equation.