This chapter focuses on the multiple places from which we draw victimization data to illustrate the scope of criminal victimization in the U.S. and around the world. This discussion includes an overview of the Uniform Crime Reports and the National Crime Victimization Survey, as well as international data sources such as the International Crime Victimization Survey and the Crime Survey for England and Wales. We also discuss the “dark figure” of crime, differences in sampling procedures, and the potential biases that may come from information gleaned from both official and self-reported estimates of victimization. The key objective is to instill in readers an appreciation for how important measurement is, particularly when different measurement strategies produce different pictures of the scope of the victimization problem. The chapter ends with a discussion of gaps and challenges, along with suggested key readings and discussion questions.