In 1983, States had PC populations ranging from 4 to 17 percent of the total prison population. A 1990 survey of prison systems to determine the extent of PC populations and assess inmate conditions of confinement was conducted by the American Correctional Association (ACA). From 190 surveys returned, 183 were usable, representing 165 State and 18 Federal facilities. Most units used for PC cases were small, averaging a design capacity of 55 inmates. The type of personal property permitted while in PC status was an indicator of the degree of normalization available. In locked units such as those typically used for PC housing, available program types were driven by the housing unit's location and size and by staffing. There are clearly more categories of PC inmates than there were 2 decades ago. Many prison administrators believe the level of violence or the underlying threat of violence in prisons is a primary factor causing the need for PC units. Legal issues relevant to PC are discussed including liability, negligence, due process, and conditions of confinement. Management of the PC problem is explored in terms of classification issues, prison gangs, drug trafficking, gambling, separation within the PC unit, support services, transfers, case monitoring, receiving and discharge, recreation, work, and visiting. Design concepts for PC units are described and illustrated. Appendixes contain ACA standards, survey responses and the survey instrument, and sample PC unit policies and procedures. 9 references, 5 tables, and 9 figures