How do we know if prevention is working? Not only is the measurement of prevention activities possible, the methodologies of “how” to measure already exist in numerous processes. Additionally, the definitions of “what” to measure have been both experienced and discussed. This article argues that measuring prevention can be accomplished by examining and evaluating the pieces that make up the whole and demonstrates that not only is prevention measurable, that measurement is well within our reach. Measuring effectiveness is not always done at the level of final outcomes. Often, the processes and systems (or outputs) that lead to preferred outcomes are measured when ultimate outcome measurement is impossible. To increase our understanding of how to combat terrorism, we need to put the argument of immeasurable prevention behind us and accept that prevention can be quantified, at least by evaluating the parts of the whole.