AbstractMembranes composed of poly(vinylpyrrolidone)‐poly(methacrylic acid) (PVP‐PMAA) complexes appear to be suitable for pervaporation of water‐n‐propanol mixtures. The membranes are selective to water. The separation factor α increases with increasing content of propanol, wPrOH, and reaches a maximum value for wPrOHat about 0.8 in the case of PVP‐rich membranes, and close to wPrOH= 1 for PMAA‐rich membranes. All membranes exhibited maximum swelling at wPrOHof ca. 0.4.At constant wPrOHof 0.8 the value of α changes in a complicated manner with the composition of the membrane. Under this condition of constant wPrOH, α runs parallel with the swelling degree. A tentative explanation is proposed for results pertaining to membranes containing not too high excesses