Responses to the New York State Department of Correctional Services' survey from 48 States, the District of Columbia, and the Federal Bureau of Prisons showed that 6 percent of the inmates under custody were classified as mentally ill and 2.5 percent as mentally retarded. The departments varied enormously in both the number and percentage of inmates classified as mentally ill or retarded. Most mentally disordered inmates had not been identified as such by the courts as part of their commitment to corrections, but had been diagnosed by corrections departments through standardized tests and clinical interviews. Inmates classified this way were usually receiving some type of psychiatric care such as psychotherapy, group therapy, and psychotropic medication within their respective institutions. Transfer to a mental health institution was not a widely used mechanism. Few institutions provided any special programming for mentally retarded inmates. An analysis of legal issues focuses on the prison inmate's legal identity, the right to treatment, the transfer of inmates for treatment, and the treatment relationship. The document's final section analyzes 15 sets of standards as they address the legal rights of mentally disordered prisoners and 5 sets of standards applying to the administration of service delivery. An executive summary emphasizes that providing adequate mental health services to mentally disordered offenders is required both by law and the standards of good administrative practice. Charts and references accompany individual chapters. A bibliography of 20 references is appended, as is a summary of prior studies on mentally ill and retarded offenders.