In a joint effort, the U.S. Department of Justice, National Institute of Corrections (NIC), National Council on Crime and Delinquency (NCCD), and the Institute on Crime, Justice, and Corrections (ICJC) selected eight State department of corrections (Connecticut, Washington, Colorado, Oregon, Florida, New Jersey, Missouri, and South Dakota) to participate in the NIC internal prison classification initiatives. Over a 7- year period, the three agencies worked with these States to develop, implement, and evaluate the impact of objective internal prison classification systems. Seven models were tested and included: Florida, Connecticut, and Colorado’s computerized objective, behavior-based model for housing and program assignments; Oregon’s model based on behavioral and compatibility indicators for female inmates; New Jersey’s behavior-based model for identifying the aggression levels of its maximum-custody inmates; Washington’s analysis of the utility of the Adult Internal Management System (AIMS) for minimum-custody inmates with long sentences; and South Dakota and Missouri’s personality-based system, the Adult Internal Classification System (AICS). Several important lessons were gained in identifying barriers in implementing these internal classification systems. Proper implementation requires increased specificity at the beginning of the planning phase and additional opportunities for further refinement. Thirteen major steps were identified in the development and implementation of an internal classification system: (1) obtain a formal commitment from the central office; (2) designate a strong project manager and establish a steering committee; (3) identify stakeholders and include them in the process; (4) define problems and set realistic goals and measurable objectives; (5) select the type of internal classification system to be adopted; (6) select the pilot site; (7) analyze current housing, work, and program assignment procedures; (8) conduct a facility program and work assignment inventory; (9) conduct a facility housing and bed inventory; (10) develop a prototype instrument and policy manual; (11) pilot test policies and instruments; (12) develop a full implementation plan; and (13) monitor and evaluate the system. In the future, internal classification system initiatives should respond to the diversity of facilities, populations, factors, and models. States should receive assistance in developing systems that are practical and feasible. References and appendix