This publication outlines a theoretical framework to guide research, policy, and action plans to combat youth violence. Research findings suggest that analyzing violence in connection with human development will provide a greater understanding of the problem. Such an analysis should trace pathways to violence in order to infuse prevention strategies into the dynamics of human development at different stages of the life course. An ecological model of life course development is proposed. This model emphasizes three key concepts to guide thinking about human development and violence prevention: (1) developmental stages, with five stages spanning infancy through adolescence; (2) transitions and pathways representing changes over the life course; and (3) nested social contexts that include family, friends, school, community, and workplace. Prevention strategies must address needs at each stage, as well as how people make transitions through them and the pathways they use. A model for action must incorporate skills, opportunities, and sanctions (positive or negative) to help people meet developmental needs. The ecological model can be used to assess the violence prevention potential of services currently provided for youth, and then a step-by-step approach can be used that first considers the developmental needs of the age group served and its social contexts. The overall goal and core assumptions should be specified, and then evaluated in light of their relationships with violence prevention. New approaches, resources, or activities can then be suggested to enhance violence prevention potential. (Contains 16 graphs, 1 figure, and 9 charts.) (SLD)