In 1996, the Los Angeles County Probation Department developed a set of six instruments to better assess offender risks and needs. Each instrument was intended to serve a specific purpose, with separate instruments used for adult and juvenile populations and release and placement decisions. The instruments were to be completed by probation staff. These instruments were tested in a pilot project by probation field staff in 1997. The probation department then asked RAND to re-examine the six instruments for instrument integrity, use of overrides, and relationship to long-term recidivism outcomes. The probation department's research staff had completed the instruments between April and December 1997 using available reports and case file information. RAND's involvement in the study began after all samples had been selected and instruments completed. The probation department gave RAND the data on instrument scores. Recidivism data were gathered at 6, 12, and 18 months after the instruments' administration. For juveniles data on the nature and date of arrest were available from the Juvenile Automated Information files. Data on adult re-arrests were unavailable, but the Adult Probation System provided the date, nature, and disposition of offenses referred to probation.