In recent years, apparent changes have evolved in the physical properties of asphalt cements used in pavement construction. Some of these properties are not controlled or are controlled only partially by AASHTO specifications. This report of the Transportation Research Board reviews all available information relating durability and performance of asphaltic concrete mixtures to the properties of the asphalt cement. Recommendations for improved test procedures and criteria are included. The report concludes that hardness of the asphalt is the property most important to pavement performance.  The report for this topic can be purchased at https://www.trb.org/news/blurb_detail.asp?id=3497