The present invention relates to a composite sheet material that is water vapor permeable and substantially liquid water impermeable. The composite sheet material includes an outer layer, a film, and a reinforcing layer and, preferably, has an ASTM D3833 water vapor transmission rate of greater than 250 g/m.sup.2/day, and a tensile strength of at least about 100 N/5 cm when tested in accordance with ASTM D5035. The sheet material is useful as a membrane for roofing, housewrap, insulation facing and in the fabrication of protective apparel.