The research design involved three phases: a mail survey to a random sampling of all U.S. jails, a follow-up telephone survey to a stratified sample of 100 of the mail survey respondents, and site visits to 10 jails during the final phase of the study. Findings show an emphasis in U.S. jails' mental health services on screening, evaluation, and suicide prevention. Also, despite numerous barriers faced by jails in providing treatment for detainees with mental illnesses, many have designed and implemented innovative programs and policies to maximize care to this group, using the limited resources available. The observed innovative programs and policies are divided into five core areas so that other jails, using the information provided, can begin to develop a mental health service strategy within the parameters of their resources. The five areas are screening, evaluation, and classification procedures; crisis intervention and short-term treatment practices; discharge planning mechanisms; court liaison mechanisms; and contracting procedures. 9 references and 4 tables