Nearly 75 percent of all detainees arrested are being set free because there is not enough evidence that they pose a threat, according to the Army. Many -- about half -- are freed within days of their arrests by the units or divisions that captured them. But thousands of others are sent to major prisons, such as Abu Ghraib, where they are waiting an average of six months before their release, according to 1st Lt. Kristy Miller, spokeswoman for the military's detention system in Iraq.

From March 2003 through early last month, 42,228 Iraqi detainees had been sent into the system, and most had been released. As of Friday, there were 12,184 in American detention, thousands of whom are also likely to be released after their cases are reviewed, given the current trend.

American officials say Iraq is the main front in the fight against terrorism. But the wide sweep for suspects in Iraq produces anti-American rage and political controversy.

Last month, in an effort to encourage Sunni Muslims to support the draft Iraqi constitution, Iraqi President Jalal Talabani asked for a mass release of detainees. The U.S. military responded by setting free 1,000 prisoners.

Those releases were approved by a standing committee of American military lawyers and employees of the Iraqi ministries of justice, interior and human rights. The committee meets three days a week to plow through hundreds of files and recommend which detainees should be set free.

Two Iraqis on the committee described common American mistakes that result in Iraqis being wrongly incarcerated. The committee members, both lawyers, were made available for interviews after a request to the Iraqi government by Cox Newspapers. The interviews were granted on the condition that the members not be identified because of the risk they would face if people know they participate in decisions about detained Iraqis.

Among the cases they described, American troops arrested one Iraqi man because he had an Arabic poster showing a beheaded man. The soldiers thought it was the sinister propaganda of terrorists and hauled him to Abu Ghraib. Months later, the Iraqis reviewing the case quickly recognized that the poster was a benign tribute to Imam Hussein, a Shiite hero beheaded in the 7th century. The committee ordered his release.

Another Iraqi was selling copies of Witness, a popular tabloid newspaper peddling gossip about the old dictatorship. Troops saw the cover photo of Saddam Hussein and took the man away for months until his case was reviewed and he was set free.

Several men in the city of Fallujah were arrested when soldiers thought an elderly woman's panicked call to her grandchild was an alert that kidnappers were nearby. She was actually attempting to shield the child from American troops.

The military says it has improved training for troops in making arrests and screening detainees, with U.S. lawyers reviewing their cases repeatedly starting from the first days after Iraqis are arrested.

"Everybody we have detained or will detain we detain for specific reasons. Based on intelligence or information, we had reason to believe that the individual was conducting an attack, was conducting activities as part of the insurgency," said coalition spokesman Maj. Gen. Rick Lynch. "I believe the Iraqi people, the population of Iraq, knows we are conducting these operations to better their environment."

But the detentions are a hot political issue in Iraq. Many political leaders -- including American allies -- have denounced the frequent arrests.

Iraqis reacted angrily in May when American troops mistakenly roughed up and arrested the leader of the largest Sunni political party, which American diplomats had been trying to entice into the government.

Saleh Hadi al-Zobai, 25, was a security guard at a truck depot when American troops last October handcuffed and hooded him, arresting him for having a Kalashnikov rifle -- standard equipment here for a security guard. He spent months in prisons, where he developed diabetes and anger toward American troops he once credited for ousting Saddam Hussein.

He recalled months in Camp Bucca, a crowded camp where rock-throwing riots would erupt. There, innocents were mixed with hardened fighters. He was released by the review board after signing a pledge not to commit violence.

"I was nervous. I was sick. I was mad. People were crying. Most had nervous breakdowns," he said. "When we talked among the prisoners, people would say it would be a crime if you got out and did not fight" the Americans.