This chapter provides a foundation for understanding the definition, types, and prevalence of older adult maltreatment. It defines the older adults as they are in federal legislation, from the Older Americans Act (OAA), as adults 60 years and older. The location of the abuse has tremendous implications for public policy and community services. If older adult maltreatment is considered endemic to the home, policies and funding will address abusive individuals; however, if abusive behaviors are viewed as occurring principally in institutions, policies will focus on quality of care. According to many common typologies, older adult maltreatment can occur in seven different types: physical, emotional or psychological, sexual, financial or other material exploitation, neglect, abandonment, or self-neglect. Ageism may be an underlying factor in older adult abuse, and it may explain why so little attention, and resources, have historically been paid to understanding and combating older adult abuse.