The lawsuit comes 10 months after the release of a damning Senate report that said the interrogation techniques had inflicted pain on al-Qaida prisoners far beyond the legal limits and did not yield lifesaving intelligence.
The suit accuses the psychologists, James E. Mitchell and John "Bruce" Jessen, of developing an interrogation program that relied on beatings, sleep deprivation, starvation, waterboarding and other methods that caused physical and psychological suffering on prisoners in CIA custody.
The suit was filed in federal court in Washington state on behalf of three former CIA prisoners. One, Gul Rahman, was interrogated in a dungeon-like Afghanistan prison called the Salt Pit, subjected to isolation, darkness and extreme cold water, and was later found dead of hypothermia.
The other two men, Suleiman Abdullah Salim and Mohamed Ahmed Ben Soud, were held in CIA prisons but were never charged with any crimes and are now free.
A 2010 Associated Press report, citing former US officials, said the CIA had promised to cover at least $5 million in legal fees for the psychologists if the program ran into trouble.
"They claimed that their program was scientifically based, safe and proven, when in fact it was none of those things. The program was unlawful and its methods barbaric," Steven Watt, a senior staff attorney with the ACLU Human Rights Program, said in a statement.