Homicide continues to be a problematic public health concern, but homicide rates have dropped considerably since the mid-1980s. This article proposes that the decrease in violence was caused by a large number of national and local violence prevention initiatives. Homicide and violence data are reviewed and the developmental dynamics of violence and homicide are discussed, noting the different tracks youth take toward violence. The risk factors that lead youth toward a violent lifestyle are compared with the protective factors that shield them from it. The principles involved in the prevention of violent behavior such as homicide are also discussed.