Historically it has been difficult to measure child maltreatment because researchers, agencies, and states all define it differently. For instance, does abuse mean that the child shows a physical injury, and if so, how do we know when the injury is not accidental? What happens if a child refuses to acknowledge the abuse, as is frequently the case, or if the child is too young to describe his or her experience? This book does three main things: It examines the history of classification and identification, provides specific suggestions for future empirical work and model development, and gives researchers an overview of how policy trends and practice can advance or impede progress in this area.