During the past decade, the knowledge of risk factors for youth gang membership has grown exponentially, as well as the breadth of literature on youth gang membership. In this review of the youth gang literature, supported by the U.S. Department of Justice, Office of Juvenile Justice and Delinquency Prevention, focus is placed on prospective longitudinal quantitative studies due to the level of proof being higher and the research design stronger. Recent research is examined on risk factors for gang membership within the context of Thornberry and colleagues’ theoretical model of gang membership, which is an extension of Thornberry’s personal interactional theory of delinquency. An attempt is made to expand this theory with a broader developmental theory of gang involvement that takes into account risk factors for delinquency that precede gang membership. It brings gang theory downward to younger pre-delinquent and delinquent levels. Gang involvement is viewed as a stepping stone in individual delinquent careers. The developmental model adds a theoretical explanation of early childhood problems and links these to problems in later childhood and subsequently to a host of risk factors for gang membership during adolescence. References