Most measurement of crime emanates from two major data sources. The first is the Federal Bureau of Investigation (FBI) Uniform Crime Report (UCR), which collects information on crimes known to the police and arrests from local and State jurisdictions. The second is the National Crime Victimization Survey (NCVS), which is a general population survey designed to discover the extent, nature, and consequences of criminal victimization. Other national surveys also provide important data on crime, victims, and offenders and focus on specific problems such as delinquency, violence against women, and child abuse. These data collection systems are beset with methodological problems such as non-reporting and false reporting, non-standard definition of events, difficulties associated with asking sensitive questions, and sampling problems. These problems are compounded by the recent interest in rare crime events, such as hate crimes; the need for attention to vulnerable sub-populations, such as very young children; and a focus on small- and local-area estimates of crime and victimization. Criminal victimization is a relatively rare event and the majority of respondents do not report any victimization. Very large general population samples are required to accurately characterize the population of offenders and victims, and detailed subgroup analyses can be problematic. Foremost among the problems of UCR arrest data is that most crimes are not reported to the police and only a small proportion of those that are reported result in an arrest. The accuracy of official data is also compromised by differences in the definitions of crimes and reporting protocols. There has been a significant lack of governmental and private interest and investment in research aimed at solving these kinds of problems. The measurement issues included improving reliability, evaluating the impact of nontraditional survey methodologies, response errors across self-report and administrative surveys, and survey packaging design. 3 figures, 4 tables, 200 references, 4 footnotes, 2 appendices