This essay considers debate over the extent to which some inmates should be isolated from others within prison, the impact of isolation on psychological well-being during confinement, and the implications for supermax prisons with 23-hour lockdown. The need for administrative segregation and solitary confinement is assessed in the context of improving the safety of individual inmates as well as preventing collective violence. These ideas are contrasted with the downside of isolation, including the possibility of compounding problems with existing mental illnesses, the development of “new” psychological problems during confinement, increased demands for psychological and psychiatric resources, and the problems posed for successful re-entry. However, contrary to some scholarly discourses, evidence to date suggests that administrative segregation does not produce dramatic negative psychological effects unless extreme conditions apply.