Every year Hot Mix Asphalt (HMA) roadways are rehabilitated by milling the existing roadway and replacing the milled portion with new HMA. As a result of this practice, a tremendous amount of reclaimed asphalt pavement (RAP) is created. The Federal Highway Administration estimates that 100 million tons of HMA is milled each year (MAPA, 2007). The Washington State Department of Transportation (WSDOT) currently allows RAP to be recycled into new HMA, but only 20% of the RAP may be used in the new material. Thus, a large portion of the milled asphalt ends up at contractors’ pits or landfills. Due to the possible reduction in product and construction cost by using RAP as base course, in addition to increasing requests by contractors to do so, WSDOT is investigating the possibility of blending RAP with virgin material for use as a base course material. This report analyzes existing studies that have examined the properties and performances of 100% RAP mixtures as well as RAP/virgin aggregate blends. In addition, this report includes a survey of 12 state DOT’s detailing current practices regarding the use of RAP as base course and any corresponding specifications and testing procedures.