Supermax prisons are large-scale facilities designed to house over 200,000 of the most violent inmates in single-cell confinement for up to 23 hours per day. While these types of facilities were once rare, now over two-thirds of States have developed supermax prisons. In order to begin to gauge the goals and effectiveness of supermax prisons, the Urban Institute engaged in an exploratory study of supermax facilities, the results of which are presented here. The research involved a review of the existing research literature, telephone interviews with 60 corrections personnel, and site visits. Findings revealed that 90 percent of wardens agreed that the goal of supermax prisons is to increase safety, order, and control and incapacitate violent and disruptive inmates. More than 80 percent agreed that supermax prisons have increased staff safety and order within institutions. The characteristics of inmates in supermax prisons are described followed by a discussion of the unintended consequences of supermax prisons, which include a false sense of security among staff and increased fear of crime among local citizens. Alternatives to supermax prisons are considered, such as increased staff training and the use of segregation cells within each facility of a prison system. Policy implications are identified and include the importance of clarifying the goals of existing and proposed supermax prisons. Future research should focus on documenting the intended and unintended effects of supermax prisons. Table, endnotes, references