Unbound materials provide a significant portion of the structural capacity of layered flexible pavement systems. Recent advances in mechanistic-empirical modeling for pavements make it now possible to predict pavement performance in terms of fundamental engineering properties such as the resilient modulus and permanent deformation characteristics. The resilient modulus and permanent deformation characteristics of four coarse-grained unbound base materials and four fine-grained natural subgrade materials are evaluated via laboratory testing in this study. Specific details of the testing protocols including differences between large vs. small specimen response, sample conditioning effects, and the influence of stress level are investigated. The material property data measured in this study provide a valuable contribution to the small but growing database of typical values as required in the forthcoming new national pavement design guide (2002 Design Guide, 2003).