The article examines the national data systems and sources used to assess the extent and seriousness of violence against women. The major sources are the Federal Bureau of Investigation's Supplementary Homicide Reports, which provide data on intimate partner homicides; the Department of Justice's National Crime Victimization Survey; three national self-report surveys; and various data from hospitals and emergency rooms. Although there are a variety of national data systems that could be used to collect data on cases of violence against women seen and/or treated by health care institutions, such data systems cannot yet provide local or national data. Self-report surveys, including the National Crime Victimization Survey and other national surveys, have yielded estimates of the rates of violence against women that vary from 7.5 to 117 per 1,000 women. The article analyzes the strengths and weaknesses of data sources, systems, and estimates. Table, note, references