Asphalt mixture stiffness is an important parameter used during pavement design and the evaluation of pavement performance. This study used the resilient modulus ( M R ) test (ASTM D7369) to measure the stiffness of several types of asphalt mixtures and various specimen types. Five types of asphalt mixtures were studied: virgin mixture without recycled materials; control mixture with recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), and warm-mix asphalt additive; and three other mixtures with RAP, RAS, and different types of recycling agents. The specimen types used in the study were field cores, on-site plant mix laboratory-compacted specimens, and reheated plant mix laboratory-compacted specimens. The objectives of the study were to assess the effect on M R values of ( a) smoothness of field core surfaces and ( b) measurement angle in field cores and laboratory-compacted specimens. In addition, the study compared the M R results for the various mixture and specimen types. The results indicated that smoothness and measurement angle had no statistically significant effect on M R at the 95% confidence level. However, the test was able to identify statistically significant differences between mixture and specimen types. Finally, a comparison between M R and dynamic modulus (DM) test (AASHTO TP79) results showed equivalent ranking of the mixtures, confirming that M R is a practical alternative to DM testing.