Estimates from the Second National Survey of Children's Exposure to Violence indicate that approximately 17.5 million youth in the United States have been exposed to violence involving a weapon in their lifetimes as witnesses or victims, or approximately one in four children. More than 2 million youth in the United States (1 in 33) have been directly assaulted in incidents where the high lethality risk weapons of guns and knives were used. Differences were noted between victimizations involving higher and lower lethality risk weapons as well as between any weapon involvement versus none. Poly-victims, youth with seven or more victimization types, were particularly likely to experience victimization with any weapon, as well as victimization with a highly lethal weapon compared with nonpoly-victims. These findings add to the field's broadening conceptualization of youth victimization, highlighting the potentially highly consequential risk factor of weapon exposure as a component of victimization experiences on the mental health of youth. Further work on improving gun safety practices and taking steps to reduce children's exposure to weapon-involved violence is warranted to reduce this problem. Data were collected as part of the Second National Survey of Children's Exposure to Violence, a nationally representative telephone survey of youth ages 2 to 17 years and caregivers (N = 4,114) conducted in 2011. (Publisher abstract modified)