This publication, along with the rest of the publications in the series, is a product of the Juvenile Detention Alternatives Initiative (JDAI) sponsored by the Annie E. Casey Foundation. The project's objectives were to eliminate the unnecessary use of secure detention for juveniles; minimize failures to appear and the incidence of delinquent behavior; redirect public finances from building new facility capacity to responsible alternative strategies; and to improve conditions in secure detention facilities. The author first lists some guiding principles to frame the discussion of ways data and information technology can support planning reform and implementing it. Examples from the JDAI sites, with actual reports, are presented, and the data required to produce the reports are described. These examples show that there were always obstacles, and the specific obstacle usually depended on the site's particular circumstances. Throughout this report, the author distinguishes between gathering and using data for planning and assessment and developing information systems that support daily operations. Finally, the report summarizes the lessons learned from the JDAI as the sites used data for planning and assessment and as they began to modernize their information systems to better support line staff. A final section describes how others can get started in collecting and using data for planning and assessment in juvenile detention reform. 3 tables, 10 figures, and 11 resources