Over the past few decades, researchers have documented positive associations between direct child maltreatment and exposure to interpersonal violence (including intimate partner violence, community violence, school violence, and media violence) and children's externalizing behavior problems. However, current family violence literature largely ignores the effects of child abuse on other children in the family. A handful of studies have focused on exposure to child abuse and documented the behavioral effects on siblings, and these studies lend support for broadening scholarship focused on this type of family violence. This article presents empirical research and theories that focus on the relationships between child physical abuse and exposure to intimate partner violence and children's externalizing behavior problems. Using this literature as a foundation, an argument is made for the need to focus on children's exposure to child physical abuse. This article presents information from the few studies that have focused on children who were exposed to the physical abuse of a sibling and offers theoretical frameworks, including social learning theory and psychological proximity, as a foundation for future research. The article concludes with a discussion of services that may be necessary for children who have been exposed to the physical abuse of a sibling, including services focused on safety and mental health. (C) 2011 Elsevier Ltd. All rights reserved.