Using data from the Rochester Youth Development Study, the authors show that trajectories of past violence predict future violence better than other more traditional measures of risk. The authors then evaluate whether factors that can be manipulated during this time can both promote less violence for all individuals as well as protect against violence among those who are most at risk for more violence. This article finds that several factors protect youth from violent behavior but not from gun or weapon carrying. Implications of these findings for future research on risk and protective factors of youth violence and for strategies for preventing such behavior are discussed.