Detainees of large urban jails have many health risks including injuries related to violence and firearms. A survey of 582 randomly selected detainees entering the Cook County Department of Corrections during the summer of 1994 found that 51 percent had previously entered hospitals for violence-related injuries, and 26 percent survived prior gunshot wounds. Patterns of firearm injuries were different from patterns of violence affecting the general population. Factors common to those with prior firearm injuries included witnessing a shooting at an early age, tattoos, previous sexually transmitted diseases, easy access to a semiautomatic weapon, and prior incarceration. Implications and prevention strategies are discussed.