A pretrial risk-assessment instrument is typically a one-page summary of the characteristics of a defendant; it produces a score that corresponds to his or her likelihood of failing to appear (FTA) in court or be rearrested prior to the completion of case processing. Typically these instruments weigh such factors as the nature of the current charge, any pending charges, the number of prior convictions resulting in jail time, prior convictions for violent crimes, FTA history, residential stability, employment/caregiver history, and drug abuse history. The risk-assessment score should be used in two decisions: whether to release or detain a defendant pretrial, and if released, the assignment of appropriate supervision conditions. Risk-assessment instruments are highly effective in predicting rates of success on pretrial release. There are a number of model instruments that have been validated in one jurisdiction and adopted by other jurisdictions after validating the imported tool on their own populations. Still, there are challenges and limitations of pretrial risk-assessment instruments. They cannot predict with accuracy a specific individual's behavior; however they provide an objective, standardized means of assessing the likelihood of pretrial failure. They have a higher accuracy than subjective assessments by even the most experienced decisionmakers. The pretrial risk-assessment instrument is an appropriate tool for deciding whether pretrial detention is needed. Other instruments are available for identifying needs that should be addressed during pretrial supervision. Data are presented on the performance of specific pretrial risk-assessment instruments, and the outcomes of their use are reported for specific jurisdictions throughout the Nation. 2 charts and 10 notes