Abstract : The Department of Defense Simulation-Based Acquisition (SBA) initiative focuses on identifying opportunities to improve materiel procurement by using information technologies to increase military utility, decrease life cycle costs, and decrease the time to develop and field the system. Implementing this initiative requires identifying the necessary analysis tools, constructing a collaborative environment, and developing a method to make timely decisions based on the results of the analysis. This paper focuses on the latter two components. In particular, it analyzes the opportunities to implement the SBA initiative during the development and analysis of the system's requirements trade space. The authors present a methodology for a holistic approach to determining the system's requirements. This methodology seeks to use models and simulations to support decisions that occur throughout the system's life cycle while in the system's concept development phase and then revisit these decisions as the program matures.