Antistrip additives are routinely used by many agencies to improve the water resistance of asphalt concrete mixtures. The effect of these additives on the properties, behavior, and performance of asphalt has received little documentation in the literature. It is often assumed that the antistrip additives are absorbed on the aggregate surface and do not interact with the asphalt. Experience in some states indicates that antistrip additives can soften the asphalt cement, and at least one state agency does make allowance for specification noncompliance (viscosity) when antistrip additives are used.