The U.S. Army Reserve (USAR) is an integral part of the U.S. Army and the country's national defense. Its mission is to provide trained Individuals who can serve as active duty soldiers when the mission calls for it. Well-trained service members are central to the USAR mission, and personnel and career management are critical to building a well-trained force. End Strength forecasts are an important input to recruiting and retention policy decisions, as well as resourcing and planning discussions with other Army components. However, generating these forecasts is a complex task due to the many paths into and out of USAR. Currently, no single model is capable of providing such estimates. The authors examined available modeling capability and identified a set of modeling tools that can estimate portions of the personnel flows into and out of USAR. Most of these tools were designed to support policy analysis, not forecast end strength. Nevertheless, with the appropriate care and caution, the estimates generated by these tools can be combined to construct the desired 24-month end strength forecasts. A detailed plan for doing so-the Integrated Modeling Concept-is the primary product of this study. Book jacket.