Evidence indicates that family violence is a major cause of subsequent delinquency. In a recent study funded by the Office of Juvenile Justice and Delinquency Prevention, researchers followed 1,000 7th and 8th grade students in Rochester, New York, for 4 years. This study found that mistreated youths who grew up in violent families were twice as likely to commit brutal acts as children from nonviolent families. Highest rates of youth violence occurred among those exposed to spouse abuse, child mistreatment, and general hostility. Nearly 80 percent of study youths reported involvement in violent delinquency, compared to 39 percent of those from nonviolent homes. Because violence permeates some families, several States are encouraging cooperation between agencies that serve abusive families. For example, Michigan, Massachusetts, and Hawaii have established programs to identify and respond effectively to both abused children and battered women. The importance of adequately preparing service professionals to deal with domestic violence is emphasized. A model law developed by the National Council of Juvenile and Family Court Judges on domestic and family violence is described.