Uses longitudinal data on more than 4,500 high school seniors and dropouts from California and Oregon to determine the prevalence of various violent behaviors among high-school-age adolescents and the co-occurrence of teenage violence with other public health problems. More than half the sample had engaged in violence in the past year, and nearly one-quarter had committed serious (predatory) violence. Violent youth were considerably more likely than their nonviolent peers to suffer from a range of public health and other problems, including drug use, drug selling, poor academic orientation, and poor mental health. Between 4 and 20% of the sample could be called "violent youth with multiple emotional and behavioral problems," depending on how liberally or stringently these behaviors were defined. Findings from this study suggest that efforts to reduce youth violence must target a broader swath than those usually identified as "high risk." Moreover, interventions must be sensitive to how adolescents differ in the kind and degree of violence they display and in the other behaviors that accompany violence.