Fluid-applied air-barrier/water-resistive-barrier membranes for use in exterior wall systems are relatively new products and are increasingly being specified and used by designers and building owners. These membranes can serve as the primary air barrier and water-resistive barrier, as well as the vapor retarder depending on the vapor permeance of the membrane. The integrity and continuity of this membrane is essential, given that this single material may perform up to three critical functions and will govern the performance of the wall system in terms of moisture migration and waterproofing. The lack of widely accepted industry standards of material property performance for these products makes it difficult for designers to compare products from different manufacturers. Further, because these products are relatively new, their long-term performance is not well established. As such, durability testing of these membranes is important to help designers and building owners anticipate long-term performance prior to specifying these products on projects. This article compares material properties and durability of 14 fluid-applied air barriers, both vapor-permeable and -impermeable products, as determined by laboratory testing. Properties tested include adhesion to common substrates, elongation, and water absorption. The laboratory testing program also addresses the durability of the membranes by testing the effect of freezing temperatures, exposure to water and UV radiation, and aging on the material properties noted above. This article discusses the development of the laboratory testing program, outlines methods of testing and accelerated weathering, and summarizes the test results.