This paper presents the results of a falling weight deflectometer (FWD) deflection analysis study performed as a part of data analysis study under the Long-Term Pavement Performance (LTPP) program. The paper presents backcalculation procedures for rigid pavements adapted in this study and discusses the results of backcalculation. Backcalculation was performed using dense liquid (DL) and elastic solid (ES) subgrade models. Although backcalculated parameters determined in this study were found to be realistic for the majority of the LTPP rigid pavement sections, this study also uncovered some limitations of the current backcalculation procedures for rigid pavements. It was noted that backcalculated values may vary significantly due to factors such as temperature at the time of testing, slab curling conditions, time of day, and time of year. Current rigid pavement backcalculation technology is inappropriate to adequately address all of these matters; however, the LTPP database provides an excellent opportunity to conduct an in-depth study.