The purpose of this workbook is to help public health program managers, administrators, and evaluators develop a joint understanding of what constitutes an evaluation plan, why it is important, and how to develop an effective evaluation plan in the context of the planning process. An evaluation plan is a written document that describes how you will monitor and evaluate your program, as well as how you intend to use evaluation results for program improvement and decision making. The evaluation plan clarifies how you will describe the "What," the "How," and the "Why It Matters" for your program. The "What" reflects the description of your program and how its activities are linked with the intended effects. It serves to clarify the program's purpose and anticipated outcomes. The "How" addresses the process for implementing a program and provides information about whether the program is operating with fidelity to the program's design. Additionally, the "How" (or process evaluation), along with output and/or short-term outcome information, helps clarify if changes should be made during implementation. The "Why It Matters" provides the rationale for your program and the impact it has on public health. This is also sometimes referred to as the "so what" question. Being able to demonstrate that your program has made a difference is critical to program sustainability. An evaluation plan is similar to a roadmap. It clarifies the steps needed to assess the processes and outcomes of a program. An effective evaluation plan is more than a column of indicators added to your program's work plan. It is a dynamic tool that should be updated on an ongoing basis to reflect program changes and priorities over time. An evaluation plan serves as a bridge between evaluation and program planning by highlighting program goals, clarifying measurable program objectives, and linking program activities with intended outcomes.