The author explains that this guide offers an introduction to problem-solving evaluation and assessment by showing police officers how to find answers to two key questions: (1) did the problem decline and (2) was the decline due to the police response to the problem? The author points out that this guide is written for officers who are familiar with the SARA (scanning, analysis, response, and assessment) problem-solving process but that no particular expertise is needed. To begin, the author notes that there are two decisions to make when evaluating and assessing a problem-solving effort. First, did the problem decline enough to cease the effort? Second, would it be worthwhile to apply the same police response to similar problems? Making either decision requires a great deal of knowledge about the problem, the police response to the problem, and how the response has been implemented. As such, the author discusses two studies to aid in the evaluation and assessment of a police response: a pre-post design and an interrupted time series design. The pre-post design helps to assess whether to cease the problem-solving effort while the interrupted time series design can also help assess whether the response would be appropriate for similar problems. To begin the process, the author suggests that two evaluations be conducted: a process evaluation and an impact evaluation. The process evaluation assesses whether the police response occurred as planned. The impact evaluation assesses what happened to the problem; did it decline? If so, why? The author offers guidance on how to prepare and conduct impact evaluations, including which measures to use and how to measure validity. Also included is a guide detailing criteria for claiming that the police response caused the decline in the problem. The appendices offer the reader practical suggestions and case studies to aid in their evaluations of the effectiveness of police responses. Figures, tables, and references