A treated vapor permeable microporous membrane includes: amicroporous membrane having a first side and a second side opposite the firstside. The membraneincludes a thermoplastic organic polymer having a polyolefin. The membranedefinesa network of interconnecting pores communicating substantially throughout themembrane. The treated membrane further includes finely divided, particulatefiller distributedthroughout the membrane and a first hydrophobic/oleophobic material over atleast aportion of the first side. A method of preparing the treated vapor permeablemicroporousmembrane is also disclosed.
