Inmate-on-inmate victimization rates were examined through official and self-report data. We checked prison records of 219 male inmates from a prison in Portugal, and estimated rates of official inmate-on- inmate victimization during a 12-month period. Of these 219 inmates, 108 agreed to participate in a self-report survey on their inmate-on- inmate victimization experiences in the last 12 months. According to official records 3.2% of the inmates were victimized, contrasting with the 78.5% prevalence rate revealed in self-report data. This high dark- figure highlights the need to implement specific strategies to prevent inmate-on-inmate victimization hence assuring the prison conditions necessary to corrections efficacy.This research was conducted at Psychology Research Centre [Centro de Investigação em Psicologia]
(UID/PSI/01662/2013), University of Minho, and supported by the Portuguese Foundation for
Science and Technology [Fundação para a Ciência e a Tecnologia] and the Portuguese Ministry
of Science, Technology and Higher Education [Ministério da Ciência, Tecnologia e Ensino
Superior] through national funds and co-financed by FEDER through COMPETE2020 under the
PT2020 Partnership Agreement (POCI-01-0145-FEDER-007653). The study was also supported by
Grant SFRH/BPD/108602/2015 from the Portuguese Foundation for Science and Technology
awarded to the second author
