Most violence prevention efforts represent thoughtful responses to the escalation of fear, violence, and disorganization in the schools. However, the lack of effectiveness data is a major reason why Congress has restricted funding for drug and violence prevention in schools to programs that have empirically demonstrated behavior changes. Evaluation can inform effective program implementation, enable a school to demonstrate to the community and potential funders the program’s usefulness, and influence policymaking. The most basic questions about an intervention program are about its results, the qualities that make it effective, and the cost effectiveness. The four types of evaluations used to address these questions are needs assessment, outcome evaluation, process or monitoring evaluation, and cost-benefit analysis. Basic components that will make the results more readily interpretable and valid are the collection of baseline outcome data before the intervention takes place; assessment, whenever possible, of a comparison group not exposed to the intervention; and random assignment of students to treatment groups or controls. 17 references