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 that affect the general population. Factors common to those with prior firearm injuries included witnessing a shooting at an early age, tattoos (usually gang-related), previous sexually transmitted diseases, easy access to a semiautomatic weapon, and prior incarceration. Obtaining research data on this issue identifies those persons at highest risk for involvement in violence and points to opportunities for prevention. Involvement in the criminal justice system may be the single best predictor of the probability that a person becomes injured through violence. Jail health care services have opportunities and obligations to intervene in many health risks and medical problems that might otherwise affect the community. Development of multidisciplinary strategies to reduce risks of violence would be appropriate. Prevention strategies must address the factors of low education, poverty, unemployment, family structure and violence, and drug abuse. In order to prevent gunshot wounds, however, additional factors should be addressed. These include treating the emotional trauma of a witnessed or experienced violent event, removing gang tattoos, providing hope for a future, reducing criminal recidivism through carefully evaluated reintegration programs, and reducing the accessibility of firearms. 5 tables and 75 references