This chapter explains why sibling abuse is generally believed to be the most common form of family violence and discusses what constitutes sibling abuse. It examines the effects of sibling abuse and how to detect sibling abuse. The chapter also discusses the laws designed to prevent or reduce sibling abuse. Sibling abuse is probably the most common form of family violence in the United States. Sibling abuse is any form of physical, mental, or sexual abuse inflicted by one child in a family unit on another. As with other types of family violence, sibling abuse can be divided into three distinct forms of abuse: physical, emotional, and sexual. The effects of sibling sexual abuse are different and distinct from the effects of stranger or acquaintance abuse. Society often accepts violence between siblings as normal. Sibling abuse can have long-term consequences for its victims.