Recent published studies clearly emphasize the importance of dynamic modulus (|E*|) testing of hot-mix asphalt concrete (HMA). The dynamic modulus is one of the fundamental inputs in the mechanistic-empirical (M-E) Design Guide developed through National Cooperative Highway Research Program (NCHRP) Project 1-37A. The current AASHTO TP62-03 specifies that the dynamic stress be adjusted to obtain: (1) axial recoverable strains between 50 and 150 microstrain; and (2) cumulative permanent strain of less than 1,500 microstrain at the end of the tests at each temperature level. The requirement is to maintain the test specimen behavior in its linear viscoelastic range during the |E*| testing regime. However, it is suspected that axial dynamic strains between 100 and 150 microstrain may produce cumulative permanent strain levels which affect the linear viscoelastic response of the material, which in turn affects the |E*| results that influence predicted pavement performance. In order to investigate the effect of the dynamic strains, a study of four |E*| tests was conducted. Two |E*| tests were performed on a set of three replicate specimens using axial dynamic strains between 50 and 100 microstrain. Another two |E*| tests were performed on a second set of three replicate specimens using axial dynamic strains between 100 and 150 microstrain. The two sets of test specimens were fabricated using the same HMA mixture. The results showed that the |E*| determined using the two dynamic strain levels were significantly different at high temperatures (38 and 54C). Based on the study results, it is recommended that axial dynamic strain levels used in E* testing be re-evaluated and possibly reduced to account for possible viscoelastic response effects.