Studies of offender treatment suggest that offenders who receive some kind of psychosocial treatment tend to better than those who do not. Research also reveals differences in the effectiveness of different types of correctional programs. Interventions based on empirically valid theories of criminal behavior that address criminogenic needs and account for offender learning styles and characteristics produce greater results, while unstructured casework, counseling, and insight-oriented and nondirective approaches tend to have less impact. In addition, research indicates that high program integrity can lead to better offender outcomes and that variations in treatment outcomes can result from methodological differences between studies. Community-based programming tends to produce greater results than programming delivered in custody. The relationship between risk and treatment failure is examined, and the effectiveness of correctional programs is discussed in relation to offender characteristics, risk and program intensity, organizational and staff characteristics, and relapse prevention. Key concepts associated with effective correctional programs are identified. 26 notes