Although many papers were published during the past decade on the coefficient of thermal expansion (CTE) and its impact on concrete pavement design, an error was recently discovered in the AASHTO TP60-00 about the calibration of the testing equipment and, consequently, determination of the concrete CTE. The new AASHTO T336-09, even though based on the TP60-00, rectifies this calibration issue. This paper presents differences between the two test methods and implications for the Long-Term Pavement Performance database and for the Mechanistic–Empirical Pavement Design Guide and for its implementation by state departments of transportation. Recommendations are provided for improvements to the AASHTO T336-09 test method.