Solid-liquid equilibria in the quaternary systems KCl-KBr-K2B4O7-H2O and KCl-KBr-K2SO4-H2O at 373 K were measured by the isothermal solution saturation method. The equilibrium solid phases, solubilities of salts, and densities of saturated solutions in the two systems were determined. The experimental data are used to plot the solubility diagrams, water content diagrams, and solution density diagrams of the two systems. It was found that both systems contain the solid solution of KCl and KBr [K(Cl,Br)], so their solubility diagrams have no invariant point, but each has a univariant curve and two crystallization regions. In the first system, the solids are K(Cl,Br) and potassium borate aquahydrate (K2B4O7 center dot 4H(2)O), and in the second system, the solids are K(Cl,Br) and potassium sulfate (K2SO4).