Highlights of the findings from this report on the solitary confinement of young offenders in jails and prisons in the United States include the following: nationwide, young offenders are subjected to solitary confinement often for weeks and months at a time; during confinement, these young offenders are often denied access to treatment, services, and programs necessary to meet their rehabilitative needs; solitary confinement of young offenders can lead to serious mental and physical health problems, along with serious developmental problems; and the use of solitary confinement is unnecessary due to the existence of alternative means for addressing problems associated with young offenders. This report examines the conditions under which young offenders are placed in solitary confinement and the effect that this has on young offenders' physical and mental well-being. Data for the report were obtained from interviews and correspondence with more than 125 individuals who were held in prisons or jails while they were under the age of 18, and corrections officials who managed jails or prisons. The data revealed that many adolescents reported being subjected to solitary confinement more than once while they were under the age of 18; that many reported struggling with serious mental health problems during their time in solitary confinement; and that several reported attempting suicide while in isolation. Other problems associated with solitary confinement include physical and developmental harm, deprivation of contact with family members, and lack of access to education and other rehabilitation programs. A set of recommendations for the use of solitary confinement with adolescent offenders is presented in the report. Appendixes