Violent behaviour within penal institutions is a very commom phenomenon that many prisoners consider inevitable. While serving a prison sentence, it is a great concren for prison officials and administration, both in terms of security within the institution, as well as in terms of the harmful effect of violent behavior on the prisoner's rehabilitation process (Friedmann, Melnick, Jiang, Hamilton, 2008). Therefore, the goal of this paper is to provide an overview of the existing knowledge about the incidence of violence in penal institutions in order to enable a better understanding of it, its patterns and impact, both on the individual and the wider community and society as a whole. For this purpose, I will list and define the types of violence that most often take place within penal institutions, analyze the models by which violent behavior is usually interpreted, define and describe factors related to violent behavior, and present known data related to violent behavior within penal institutions of the Republic of Croatia. Later, I will look at the position of violent prisoners within the prison hierarchy, and ultimately describe the consequences that violence has for the individual, the institution itself, and the wider social community.