The purpose of this manual is to provide a framework for thinking about NED costs and their various uses by the Corps of Engineers. The intent of this manual is to furnish the reader with the tools necessary to understand what NED costs are, how they are used and how they differ from other definitions of costs. To understand NED costs it is essential that the nature of these other costs be considered as well. Costs are used by the Corps in two primary ways. First, NED costs are used to make decisions about the relative economic efficiency of alternative actions. Once such a decision has been made, dollar costs become the focus of Corps elements as they refine construction cost estimates, prepare budgets and let contacts. Non-Federal partners focus on their dollar costs as they plan for financing their share of project costs. Thus, what we will call implementation decisions require that attention be paid to a different set of costs. Through the focus of this manual is distinctly on NED costs, other costs commonly used by the Corps will be discussed as appropriate.