Jail inmates represent a high-risk, multineed population. Why do some jail inmates not access available programs and services? Drawn from a longitudinal study, 261 adults were assessed shortly upon incarceration and reassessed prior to transfer or release from a county jail. Of the participants in need of treatment, 18.5% did not participate in any formal treatment programs or religious programs and services. Untreated inmates were disproportionately young and male and less likely to report preincarceration cocaine dependence. Treatment participation varied little as a function of race or symptoms of mental illness. The most common reason for nonparticipation was the belief that one would not be around long enough to participate in programs. Other reasons were both institution-related and person-related in nature, including doubts about treatment efficacy, stigma concerns, lack of motivation, and lack of programs, especially addressing mental illness.