The report is based on the testimonies of 19 prisoners, including 17 who are currently being held in isolation and two who were held in isolation in the past and who have since been released. The majority of the testimonies were received from sentenced prisoners. The testimonies were received by using a questionnaire on prison conditions, medical (including psychiatric) treatment, and communication with the world within and outside the prison. The report is also based on applications for assistance received by PHR-Israel and Addameer from prisoners who were or are being held in isolation; on medical, including psychiatric files of prisoners in isolation; and on visits made by PHR-Israel's volunteer psychiatrists to isolated prisoners.