This knowledge base on "what works" to change offenders features three core principles: risk, needs, and responsivity. The risk principle refers to the identification of personal attributes or circumstances that predict reoffending. This principle suggests that the most intensive correctional treatment services should target the highest risk population. The principle of classification according to needs refers to targeting the needs that underlie the specific criminal behaviors of the individual. These needs may include changing antisocial attitudes, reforming feelings and values, and addressing skill and behavioral management deficiencies. Programs should be designed to address these various needs. Responsivity is the third core principle. It refers to the delivery of an intervention that matches the abilities and styles of the client. Based on these principles, an ideal model for reentry programs should include three or more phases. The first phase would begin in the institution with the delivery of services that target the inmate's needs. The second phase would begin as the inmate is released from the institution. The inmate's risks and needs may change significantly as he/she enters the community. Ideally, the individual would continue with treatment services and case plans that would be updated and modified as needed. The final phase of the reentry model is an aftercare or relapse prevention phase in which clients receive ongoing support and services that address their needs. Reentry programs that fail to develop clear goals and objectives, use effective classification systems, rely on appropriate theoretically relevant models, and plan for relapse will inevitably fail. 77 references