Information was collected between April 1994 and December 1995 by means of observations in prisons and interviews of 1,566 inmates in two adult male prisons and two male young offender institutions, 61 victims and 31 perpetrators, and 111 staff members. Results revealed that 46 percent of young offenders and 30 percent of adults had been assaulted, robbed, or threatened with violence in the previous month. Nevertheless, most inmates felt safe most of the time. In addition, those who victimized others were likely to have been victimized themselves. Moreover, previous custodial experience increased the likelihood of being a victimizer but not the likelihood of being a victim. Furthermore, very few incidents were reported to staff, mainly due to fear of retaliation and the feeling that the inmate had nothing to gain. Staff were sometimes poorly informed about national policy and local initiatives to address the problem. Findings indicate that preventive strategies should be applied throughout the prison system. Actions should include conversion of four-person dormitories to double cells, property marking, dissemination of information to staff, appropriate procedures for separating at-risk inmates to dedicated units for victimizers or victims, and victim support. Figures