This chapter emphasizes the importance of linking an injury intervention with an evaluation plan at the outset. Evaluation is often described as having one or more of three purposes: to establish or clarify program effectiveness; to improve program implementation; and to address administrative needs. Logic or causal models suggest where to intervene. Subsequently, it is helpful to have the specific implementation intervention strategies developed on the basis of conceptual planning models. The level (practice, organization, and/or community) at which the intervention is applied, plays a major part in dictating the design of the evaluation. The chapter discusses two broad categories to describe evaluation: process evaluation and outcome evaluation. The chapter summarizes the Seattle, Washington area bicycle safety helmet campaign and the statewide childhood injury prevention program (SCIPP) in Massachusetts to demonstrate some of the choices entailed in selecting process and outcome measures.