Low pressure liquid–liquid demixing data for polystyrene dissolved in 76 different one‐component solvent systems are reviewed and correlated. The phase diagrams are discussed. With only one exception the molecular weight of each solvent is less than that of two polystyrene monomer units. A new relation is developed which quantitatively correlates the area of solubility lying between the UCS and LCS demixing curves in the (Tc, Mw−1/2) projection with solvent solubility parameters. ©1996 American Institute of Physics and American Chemical Society.