There are a great many types of violence prevention programs in schools, and many are demonstrating signs of success. Funders will not provide resources for programs, nor will schools know how to choose them, unless quality evaluation data are available to show their effectiveness and promise. Resources to conduct a meaningful evaluation are often lacking, but evaluation can inform the implementation of a program, enable a school to demonstrate the value of the program, and influence the formation and implementation of social policy. Four basic types of evaluation can be integrated into the existing structure of most schools and programs. The first is needs assessment, or formative evaluation, which helps the school determine its needs regarding a violence prevention program. Examples of types of needs assessment are given. The second type of evaluation is called outcome evaluation. It answers the question of what has changed because of the intervention. A third type of evaluation is a process evaluation, which attempts to address the questions of what works best and why it works. The last type of basic evaluation is cost-benefit analysis, which addresses questions of cost effectiveness. In any evaluation, there are three basic strategies for collecting information about program effectiveness. These are: (1) collection of outcome data before the intervention is implemented; (2) assessment, whenever possible, of a comparison group of students, classes, or schools, not exposed to the intervention; and (3) random assignment of students to treatment groups or controls. A comprehensive evaluation program is a major component of those violence prevention programs that have been shown to be successful. (Contains 17 references.) (SLD)