They say they are revealing specific details of the techniques, and their impact on confessions, because the public needs to know the direction their agency has chosen. All gave their accounts on the condition that their names and identities not be revealed. Portions of their accounts are corrobrated by public statements of former CIA officers and by reports recently published that cite a classified CIA Inspector General's report.

Other portions of their accounts echo the accounts of escaped prisoners from one CIA prison in Afghanistan.

"They would not let you rest, day or night. Stand up, sit down, stand up, sit down. Don't sleep. Don't lie on the floor," one prisoner said through a translator. The detainees were also forced to listen to rap artist Eminem's "Slim Shady" album. The music was so foreign to them it made them frantic, sources said.

Contacted after the completion of the ABC News investigation, CIA officials would neither confirm nor deny the accounts. They simply declined to comment.

The CIA sources described a list of six "Enhanced Interrogation Techniques" instituted in mid-March 2002 and used, they said, on a dozen top al Qaeda targets incarcerated in isolation at secret locations on military bases in regions from Asia to Eastern Europe. According to the sources, only a handful of CIA interrogators are trained and authorized to use the techniques:

1. The Attention Grab: The interrogator forcefully grabs the shirt front of the prisoner and shakes him.

2. Attention Slap: An open-handed slap aimed at causing pain and triggering fear.

3. The Belly Slap: A hard open-handed slap to the stomach. The aim is to cause pain, but not internal injury. Doctors consulted advised against using a punch, which could cause lasting internal damage.

4. Long Time Standing: This technique is described as among the most effective. Prisoners are forced to stand, handcuffed and with their feet shackled to an eye bolt in the floor for more than 40 hours. Exhaustion and sleep deprivation are effective in yielding confessions.

5. The Cold Cell: The prisoner is left to stand naked in a cell kept near 50 degrees. Throughout the time in the cell the prisoner is doused with cold water.

6. Water Boarding: The prisoner is bound to an inclined board, feet raised and head slightly below the feet. Cellophane is wrapped over the prisoner's face and water is poured over him. Unavoidably, the gag reflex kicks in and a terrifying fear of drowning leads to almost instant pleas to bring the treatment to a halt.

According to the sources, CIA officers who subjected themselves to the water boarding technique lasted an average of 14 seconds before caving in. They said al Qaeda's toughest prisoner, Khalid Sheik Mohammed, won the admiration of interrogators when he was able to last between two and two-and-a-half minutes before begging to confess.

"The person believes they are being killed, and as such, it really amounts to a mock execution, which is illegal under international law," said John Sifton of Human Rights Watch.

The techniques are controversial among experienced intelligence agency and military interrogators. Many feel that a confession obtained this way is an unreliable tool. Two experienced officers have told ABC that there is little to be gained by these techniques that could not be more effectively gained by a methodical, careful, psychologically based interrogation. According to a classified report prepared by the CIA Inspector General John Helgerwon and issued in 2004, the techniques "appeared to constitute cruel, and degrading treatment under the (Geneva) convention," the New York Times reported on Nov. 9, 2005.

It is "bad interrogation. I mean you can get anyone to confess to anything if the torture's bad enough," said former CIA officer Bob Baer.

Larry Johnson, a former CIA officer and a deputy director of the State Department's office of counterterrorism, recently wrote in the Los Angeles Times, "What real CIA field officers know firsthand is that it is better to build a relationship of trust … than to extract quick confessions through tactics such as those used by the Nazis and the Soviets."

One argument in favor of their use: time. In the early days of al Qaeda captures, it was hoped that speeding confessions would result in the development of important operational knowledge in a timely fashion.

However, ABC News was told that at least three CIA officers declined to be trained in the techniques before a cadre of 14 were selected to use them on a dozen top al Qaeda suspects in order to obtain critical information. In at least one instance, ABC News was told that the techniques led to questionable information aimed at pleasing the interrogators and that this information had a significant impact on U.S. actions in Iraq.

According to CIA sources, Ibn al Shaykh al Libbi, after two weeks of enhanced interrogation, made statements that were designed to tell the interrogators what they wanted to hear. Sources say Al Libbi had been subjected to each of the progressively harsher techniques in turn and finally broke after being water boarded and then left to stand naked in his cold cell overnight where he was doused with cold water at regular intervals.

His statements became part of the basis for the Bush administration claims that Iraq trained al Qaeda members to use biochemical weapons. Sources tell ABC that it was later established that al Libbi had no knowledge of such training or weapons and fabricated the statements because he was terrified of further harsh treatment.

"This is the problem with using the waterboard. They get so desperate that they begin telling you what they think you want to hear," one source said.

However, sources said, al Libbi does not appear to have sought to intentionally misinform investigators, as at least one account has stated. The distinction in this murky world is nonetheless an important one. Al Libbi sought to please his investigators, not lead them down a false path, two sources with firsthand knowledge of the statements said.

When properly used, the techniques appear to be closely monitored and are signed off on in writing on a case-by-case, technique-by-technique basis, according to highly placed current and former intelligence officers involved in the program. In this way, they say, enhanced interrogations have been authorized for about a dozen high value al Qaeda targets -- Khalid Sheik Mohammed among them. According to the sources, all of these have confessed, none of them has died, and all of them remain incarcerated.

While some media accounts have described the locations where these detainees are located as a string of secret CIA prisons -- a gulag, as it were -- in fact, sources say, there are a very limited number of these locations in use at any time, and most often they consist of a secure building on an existing or former military base. In addition, they say, the prisoners usually are not scattered but travel together to these locations, so that information can be extracted from one and compared with others. Currently, it is believed that one or more former Soviet bloc air bases and military installations are the Eastern European location of the top suspects. Khalid Sheik Mohammed is among the suspects detained there, sources said.

The sources told ABC that the techniques, while progressively aggressive, are not deemed torture, and the debate among intelligence officers as to whether they are effective should not be underestimated. There are many who feel these techniques, properly supervised, are both valid and necessary, the sources said. While harsh, they say, they are not torture and are reserved only for the most important and most difficult prisoners.

According to the sources, when an interrogator wishes to use a particular technique on a prisoner, the policy at the CIA is that each step of the interrogation process must be signed off at the highest level -- by the deputy director for operations for the CIA. A cable must be sent and a reply received each time a progressively harsher technique is used. The described oversight appears tough but critics say it could be tougher. In reality, sources said, there are few known instances when an approval has not been granted. Still, even the toughest critics of the techniques say they are relatively well monitored and limited in use.

Two sources also told ABC that the techniques -- authorized for use by only a handful of trained CIA officers -- have been misapplied in at least one instance.

The sources said that in that case a young, untrained junior officer caused the death of one detainee at a mud fort dubbed the "salt pit" that is used as a prison. They say the death occurred when the prisoner was left to stand naked throughout the harsh Afghanistan night after being doused with cold water. He died, they say, of hypothermia.

According to the sources, a second CIA detainee died in Iraq and a third detainee died following harsh interrogation by Department of Defense personnel and contractors in Iraq. CIA sources said that in the DOD case, the interrogation was harsh, but did not involve the CIA.

The Kabul fort has also been the subject of confusion. Several intelligence sources involved in both the enhanced interrogation program and the program to ship detainees back to their own country for interrogation -- a process described as rendition, say that the number of detainees in each program has been added together to suggest as many as 100 detainees are moved around the world from one secret CIA facility to another. In the rendition program, foreign nationals captured in the conflict zones are shipped back to their own countries on occasion for interrogation and prosecution.

There have been several dozen instances of rendition. There have been a little over a dozen authorized enhanced interrogations. As a result, the enhanced interrogation program has been described as one encompassing 100 or more prisoners. Multiple CIA sources told ABC that it is not. The renditions have also been described as illegal. They are not, our sources said, although they acknowledge the procedures are in an ethical gray area and are at times used for the convenience of extracting information under harsher conditions that the U.S. would allow.

ABC was told that several dozen renditions of this kind have occurred. Jordan is one country recently cited as an "emerging" center for renditions, according to published reports. The ABC sources said that rendition of this sort are legal and should not be confused with illegal "snatches" of targets off the streets of a home country by officers of yet another country. The United States is currently charged with such an illegal rendition in Italy. Israel and at least one European nation have also been accused of such renditions.