Phase diagrams of aqueous two-phase systems composed of poly(ethylene) glycol (PEG) 6000 g.mol(-1), lithium sulfate, sodium sulfate, and magnesium sulfate or zinc sulfate were determined at (283.15, 298.15, and 313.15) K. The effect of temperature on binodal position was not significant, indicating a small enthalpic contribution associating to the phase segregation. The ability of four sulfate salts to induce the formation of the biphasic system with PEG 6000 is as follows: ZnSO(4) > MgSO(4) > Na(2)SO(4) > Li(2)SO(4).