Recent statistics indicate that injection drug users (IDUs) and crack cocaine users are increasingly coming into contact with the criminal justice system. A number of these individuals engage in high risk behaviors associated with the transmission of the AIDS virus. This study examined HIV risk behaviors, including needle use and sexual practices, in conjunction with the length of time in jail or prison among 879 Midwestern non-in-treatment IDUs. A number of HIV high-risk variables were found to be significantly related to IDUs' length of time in jail, including those who (1) initiated drug injection at an early age, (2) had multiple sex partners (3) had a history of an STD, (4) were daily drug users, 5) daily injected cocaine, heroin, or speedball, (6) did not consistently use condoms, and (7) used "dirty" needles. Our data indicated that street IDUs with the highest HIV risk behaviors were those most likely to spend more time in jail. Because they reach a larger number of at-risk IDUs, the criminal justice system appears to be the most logical place for the implementation of drug and AIDS prevention/intervention programs. Public health initiatives on HIV risk behaviors should have priority status in the penal institutions.