The use of administrative segregation in prison is a controversial correctional policy. Proponents argue this type of housing is necessary for maintaining institutional safety and order, whereas critics contend it is damaging to inmate mental health. Despite the increase in academic attention over the last decade, there is much that remains unknown about the uses and effects of this practice. This study addresses this gap in knowledge by content-analyzing the administrative segregation policies of 48 state and federal prison systems. The results provide evidence of consistency and discrepancy across key elements of these policies, including placement criteria and review procedures. Findings further highlight how basic information regarding mental health provisions and conditions of confinement are missing from a substantial number of policies. This investigation emphasizes a need for more governmental accountability and transparency in the use of this correctional policy and identifies several areas for future research.