Changes over time in the levels and patterns of crime have significant consequences that affect not only the criminal justice system but also other critical policy sectors. Yet compared with such areas as health status, housing, and employment, the nation lacks timely information and comprehensive research on crime trends. Descriptive information and explanatory research on crime trends across the nation that are not only accurate, but also timely, are pressing needs in the nation’s crime-control efforts. In April 2007, the National Research Council held a two-day workshop to address key substantive and methodological issues underlying the study of crime trends and to lay the groundwork for a proposed multiyear NRC panel study of these issues. Six papers were commissioned from leading researchers and discussed at the workshop by experts in sociology, criminology, law, economics, and statistics. The authors revised their papers based on the discussants’ comments, and the papers were then reviewed again externally. The six final workshop papers are the basis of this volume, which represents some of the most serious thinking and research on crime trends currently available.