Phase diagram and (liquid + liquid) equilibrium (LLE) data for the (NaNO3 + polyethylene glycol 4000 (PEG 4000) + H2O) system have been determined experimentally at T= (288.15 and 308.15) K. The effects of temperature on the binodal curves and tie-lines have been studied and it was found that an increasing in temperature caused the expansion of two-phase region. The Chen-NRTL. modified Wilson and UNI-QUAC models were used to correlate the experimental tie-line data. The results show that the quality of fitting is better with the UNIQUAC model. (C) 2011 Elsevier Ltd. All rights reserved.