An estimated 17000 people were imprisoned at Security Prison 21 (S-21), also known as Tuol Sleng, during the Khmer Rouge regime in Cambodia 1975-79. Of those there are only twelve known survivors. Photographs were taken of of the prisoners and more than 5000 photos have been scanned and published on the website of Yale University as a part of the research of the The Cambodian genocide program; "The photographs are displayed in this section of the Cambodian Genocide Database, along with facilities for CGDB users to suggest names and other biographical data for unknown victims they may recognize."

Also search Yale GSP Biographical database for confessions signed in Tuol Sleng from Tuol Sleng Catalogue of Confessions (Cornell University) (CU-TS): CBIO Database search

More information about S-21, Toul Sleng