[Page 659]Violent victimization of inmates is a long-standing problem in prisons worldwide. This entry provides an overview of institutional violence toward offenders, which is defined as instrumental (proactive) or expressive (reactive) aggression directed at jail, prison, or other inmates by either fellow inmates or correctional employees. Instrumental violence fulfills an ulterior motive (e.g., manipulation, intimidation, or dominance), whereas expressive violence occurs in response to a negative emotional state (e.g., anger, fear, or frustration). Physical injuries need not occur to satisfy this definition of institutional violence; in fact, sexual victimization of inmates, which may not even involve physical contact between the victim and perpetrator, is a major concern for correctional administrators.