These offenders include defendants found not guilty by reasons of insanity, defendants found not competent to stand trial, persons adjudicated as guilty but mentally ill, convicted offenders who display symptoms of mental illness while serving a sentence, defendants being examined for criminal responsibility, and others. The study examines the nature and characteristics of these facilities, their patient populations, their staff, security conditions, treatment programs, and administrative or operational problems. Data sources included legal and library research, responses from 127 facilities that completed a mailed questionnaire, and detailed telephone interviews and observations gathered further in 60 facilities. Field interviews and observations gathered further information from 11 facilities representing a variety of legal and organizational situations. Study data were gathered in 1981 and 1982. Findings indicated the existence of appropriate treatment services and the need for more effective administrative support. Data tables, appended tables, and lists of 27 court cases and 57 references.