Asphalt mixture stiffness is an important parameter used during pavement design and the evaluation of pavement performance. This study used the resilient modulus ( MR) 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 MR 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 MR results for the various mixture and specimen types. The results indicated that smoothness and measurement angle had no statistically significant effect on MR at the 95% confidence level. However, the test was able to identify statistically significant differences between mixture and specimen types. Finally, a comparison between MR and dynamic modulus (DM) test (AASHTO TP79) results showed equivalent ranking of the mixtures, confirming that MR is a practical alternative to DM testing.