A survey of 1,566 male inmates in two adult prisons and two young offender institutions was conducted to measure levels of six types of victimization: assault, robbery, threat, insult, exclusion, and cell theft. Interviews were also conducted with 60 inmates who reported that they had recently been victimized and with 31 inmates who said they victimized others. A close examination of 96 prison assaults showed how activities considered routine in custody increased the risk of assault. Prison assaults were diverse and could not be subsumed under a single explanation. Nonetheless, some common factors in prison assaults could be identified. Victims contributed to their victimization through facilitation or precipitation by gaining a reputation for vulnerability and by increasing the aggressor's sense of impunity. Participant interpretations of events showed that there may be good reasons for an inmate deliberately putting himself at risk of being attacked. 21 references