Jail inmates represent a high-risk, multi-need 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 re-assessed 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 pre-incarceration cocaine dependence. Treatment participation varied little as a function of race or symptoms of mental illness. The most common reason for non-participation 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.