The combination of local, State, and Federal arrest records with local and State custody records provides a more complete criminal history data base than previously available. In particular, the inclusion of local custody records allows Louisiana officials to measure actual jail time served, including readmissions for probation and parole violation. The analysis of jail incarceration data should significantly improve the estimation of incapacitation effects. Official data for the New Orleans Offender Study include information taken from various criminal justice data bases: New Orleans jail information management system (STARS), New Orleans Police Department's arrest history system (MOTION), Louisiana adult penitentiary and probation/parole information system (CAJUN), Louisiana juvenile corrections information system (JIRMS), Louisiana criminal history system (FINDEX), and Federal Bureau of Investigation rap sheets. Procedures involved in the collection, coding, and analysis of data and the resulting computerized data files are detailed.