Different kinds of negatively charged membranes, namely poly (acrylonitrile-co-acrylic acid) (AN-AAc), sulfonated polysulfone (SPSF) and sulfonated polyethersulfone (SPES) membranes, were prepared by changing the contents of carboxyl and sulfonate groups in the membrane polymers, Using the prepared membranes, sorption and pervaporation experiments were conducted at 333 K in the mixtures of water and ethanol, In evaluating the sorption and pervaporation properties of these membranes, the values of Delta H-WM and Delta H-EM, which are the difference in solubility parameter between water and membrane polymer and that between ethanol and membrane polymer, respectively, are defined, Irrespective of the kind of membrane examined, a linear relation is observed between logarithmic values of selective sorption factor of water to ethanol, beta(W)/(E), and (Delta H-EM/Delta H-WM), as well as between those of separation factor, alpha(W/E) and (Delta H-EM/Delta H-WM). It is found that the values of beta(W/E) for cellulose acetate and polyion complex membranes can be evaluated from the relationships obtained in the AN-AAc, SPSF and SPES membranes.