A study of the performance of Continuously Reinforced Concrete Pavement (CRCP) constructed on the Interstate highway system in Illinois has-been conducted. The major purpose is to determine the types, severities, amounts, and causes of distress. This information will then be used to develop optimum maintenance procedures to repair the distress that occurs, and preventative maintenance procedures to reduce the rate of distress occurrence. The distress data collected can also be used to update CRCP design procedures. Approximately 1230 miles of Interstate highway was surveyed, consisting of 7 to 10 in. (17-25 cm) slabs over granular and stabilized subbases. Distress found includes edge punchouts, steel ruptures, "D" cracking, blowups, construction joint failures, lug rotation, longitudinal cracking, distress related to construction problems, pumping, and shoulder deterioration. Heavy truck loads, excess free moisture, deicing salts, construction practice and poor aggregate quality in the CRCP slab are the major factors causing distress. CRCP slab thickness and foundation support have a very significant effect on structural distress development. "D" cracking is causing severe deterioration of several projects. Overall, the performance of the thicker CRCP slabs (i.e., 9-10 in.) has been very good under heavy truck traffic; however, the performance of many sections of thinner CRCP (i.e., 7-8 in.) has been poor, and is showing an accelerated rate of distress development over time. The amount of distress expected to occur, and the maintenance effort required in the next several years points strongly toward a need for the development of more efficient and durable ways of maintaining CRCP.