The U.S. Supreme Court upheld the practice of double-celling, or placing two persons in a cell designed for one, so long as the totality of conditions within a prison do not violate a 'contemporary standard of decency.' Although recent research studies do not directly address the question of double-celling, it is recognized as one of the most stringent forms of overcrowding. These studies link prison overcrowding to increases in violent incidents, particularly among younger adult offenders in long-term facilities. Inmate health problems, both perceived and real, are worse in overcrowded conditions, and institutional security is more vulnerable. Some writers point to inmates' need for privacy and personal space, and others describe cell and circulation area size as important concerns, especially for unsentenced persons rarely leaving the cell block. In general, the longer the length of confinement or duration of incarceration, the worse will be the persons' response to overcrowding. Employee performance may also slip in overcrowded situations. Double-celling in long-term facilities may only be acceptable in emergencies. Reference notes are appended. (Author summary modified)