As part of the Office of Juvenile Justice and Delinquency Prevention (OJJDP) Comprehensive Gang Model, this guide was published to assist in evaluation of a community's youth gang problem. The Model requires that these strategies be delivered in a focused manner, based on a thorough assessment of the current gang problem in a community, its potential causes, and contributing factors. This guide was developed to assist policymakers, practitioners, and community leaders in assessing and understanding their youth gang problem and developing an integrated plan to reduce gang crime in their community. It was meant specifically to assist those individuals who would conduct the assessment, as well as those who would oversee the assessment effort and planning process. The guide provides a blueprint for an in-depth assessment and guidance throughout the process, and was developed with the five core strategies of OJJDP's Comprehensive Gang Model in mind: Community Mobilization, Opportunities Provision, Social Intervention, Suppression, and Organizational Change and Development. A major portion of this guide describes the data variables, sources, and data-collection instruments, as well as sources of perceptual and anecdotal data. It also provides suggestions on how to organize and analyze the data, and guidelines for preparation of the Assessment Report. Other portions of this guide define gang and gang crime; analyze risk factors for gang membership; and examine issues of confidentiality and consent, and other information relevant to conducting the assessment. Tables, references