The use of reclaimed asphalt pavement (RAP) as a base layer is increasing as quality aggregate becomes scarcer and more expensive. Moisture content is known to have a great impact on the resilient modulus (M sub R) of granular materials, and several researchers have devoted effort to develop and verify analytical models to describe that impact. Limited work has been done to quantify the effect of moisture content on RAP as a base layer. It has not been determined whether the existence of aged binder will allow designers to use the same analytical models developed for granular materials. This study investigated the effect of moisture content on the M sub R of a base layer that contained RAP, compared the effect of moisture content on RAP with the effect on typical base material, and reviewed the literature to select a model that would analytically predict changes in the M sub R of untreated RAP as a result of changes in moisture content.