Prison violence. Definition, assessment and explanationPrison violence is a fundamental problem for all prison systems in the world. It compromises thehuman rights, security, and integrity of the lives of the inmates and prison officers, affects theeffectiveness of programs, recidivism and economic costs in society. Despite its relevance, prisonviolence has been little studied and the scarcity of studies becomes particularly serious in contextswhere knowledge is more necessary. The objective of this study is to revise the specialized literatureon violence in prisons to discuss its most relevant conceptual and methodological problems. Firstly,the violence definition problem in the penitentiary settings will be discussed. Secondly, the mainchallenges when attempting to measure the phenomenon will be examined. Thirdly, we will revisedifferent theories and explanations of violence and