Over the last year this newspaper has shone the bright light of hindsight on decisions that led the United States into Iraq. We have examined the failings of American and allied intelligence, especially on the issue of Iraq's weapons and possible Iraqi connections to international terrorists. We have studied the allegations of official gullibility and hype. It is past time we turned the same light on ourselves.

In doing so -- reviewing hundreds of articles written during the prelude to war and into the early stages of the occupation -- we found an enormous amount of journalism that we are proud of. In most cases, what we reported was an accurate reflection of the state of our knowledge at the time, much of it painstakingly extracted from intelligence agencies that were themselves dependent on sketchy information. And where those articles included incomplete information or pointed in a wrong direction, they were later overtaken by more and stronger information. That is how news coverage normally unfolds.

But we have found a number of instances of coverage that was not as rigorous as it should have been. In some cases, information that was controversial then, and seems questionable now, was insufficiently qualified or allowed to stand unchallenged. Looking back, we wish we had been more aggressive in re-examining the claims as new evidence emerged -- or failed to emerge.

The problematic articles varied in authorship and subject matter, but many shared a common feature. They depended at least in part on information from a circle of Iraqi informants, defectors and exiles bent on ''regime change'' in Iraq, people whose credibility has come under increasing public debate in recent weeks. (The most prominent of the anti-Saddam campaigners, Ahmad Chalabi, has been named as an occasional source in Times articles since at least 1991, and has introduced reporters to other exiles. He became a favorite of hard-liners within the Bush administration and a paid broker of information from Iraqi exiles, until his payments were cut off last week.) Complicating matters for journalists, the accounts of these exiles were often eagerly confirmed by United States officials convinced of the need to intervene in Iraq. Administration officials now acknowledge that they sometimes fell for misinformation from these exile sources. So did many news organizations -- in particular, this one.