Microfiltration membranes from a polymeric composition consisting of poly(vinyl chloride) and co-poly(butadiene-acrylonitrile) were prepared. It was found that with an increase in the co-poly(butadiene-acrylonitrile) concentration in the blend, the operating membrane was converted from a viscoelastic material to a purely elastic one. The blend membrane showed better elastic properties under tensile stress than the pure poly(vinyl chloride) membrane did. The enhancement of the mechanical properties due to the addition of the elastomer was accompanied by a small deterioration of the flux.