The research collected information by means of a mail survey to a random sample of all jails, a telephone survey to a stratified sample of 100 of the jails that responded to the mail survey, and site visits to 10 jails. The 1-page mail survey received responses from 1,036 jails, for a 61- percent response rate among the 1,706 jails to which the survey was mailed. The stratified sample was selected from jails that had rated their mental health services as very effective; 10 were chosen for site visits due to their particularly noteworthy practices. Results revealed much emphasis in the jails' mental health services on screening, evaluation, and suicide prevention. In addition, despite many barriers that jails experience in providing treatment for detainees with mental illnesses, many jails have designed and implemented innovative programs and policies for these detainees. The innovative programs were grouped into five core areas: (1) screening, evaluation, and classification procedures; (2) crisis intervention and short-term treatment practices; (3) discharge planning mechanisms; (4) court liaison mechanisms; and (5) contracting procedures. Findings indicated that these jails' policies and procedures represent promising strategies that can be adapted to individual communities to help all jails develop mental health services that meet constitutional standards and the needs of the individual jail, its detainees, and its community. Tables and 16 references (Author abstract modified)