"Administrative segregation, the preferred term among correctional administrators, refers to both a classification and a type of unit. There are at least three distinct types of segregation: administrative segregation, disciplinary segregation, and protective ... Any of these types of segregation might involve a regimen of solitary (or near solitary) confinement. Importantly, it is the increased use of solitary confinement, not segregation per se, that troubles those with concerns about contemporary correctional practice, and it is solitary confinement that has received the most attention in the research literature ... Within the limited empirical knowledge base in this area, researchers have not always agreed on the areas of research that warrant review and evaluation, or they have been unable to draw conclusions from studies employing various methodologies. Further, for many researchers studying solitary confinement the practice raises not only empirical questions, but also moral and ethical concerns. In a literature base replete with highly charged emotions, interpreting the evidence base, and separating evidence from strongly held beliefs have become difficult. This paper attempts to describe the research in enough detail that the reader can reach his or her own conclusions around the current state of administrative segregation" (p. 1, Executive Summary). Sections comprising this report include: introduction; brief history of administrative segregation; contemporary use of administrative segregation; issues related to use of solitary confinement-juveniles, control of gangs, and mental illness; court decisions and consent decrees; the utility and effects of administrative segregation--violence; the psychological and behavioral effects of solitary confinement; the future of administrative segregation; and conclusion. Appendixes include: Table A1-Administrative Segregation in the Federal Bureau of Prisons (BOP); Table A2-Percentage of Custodial Population (Both Sexes) In Administrative Segregation (Ad Seg) and Restrictive Housing; and Table A3-Goals and Intended Impacts Associated with Supermax Prisons.