LEXINGTON, Ky., July 9— It began with a joke.

Deep into a speech on journalism ethics in May, John S. Carroll, now the editor of The Los Angeles Times, told University of Oregon students about his days as editor of The Herald-Leader in Lexington, Ky., where the running gag among newsroom staff members was that they should print the following ''clarification'':

''It has come to the editor's attention that The Herald neglected to cover the civil rights movement. We regret the omission.''

Mr. Carroll, who edited the paper from 1979 to 1991, said he was just trying to underscore the difficulty of correcting major mistakes. ''I did it primarily to get a laugh,'' he said in an interview. ''I didn't intend to challenge the paper to do anything.''

But a challenge is precisely what it became. When The Herald-Leader's enterprise editor, John Voskuhl, read Mr. Carroll's speech online a few days later, a light bulb went off in his head and he fired off an e-mail message to the paper's new editor asking for permission pick up the gauntlet.

''I knew we had skeletons in our closet,'' Mr. Voskuhl said.

On July 4, readers of The Herald-Leader saw the results of the paper's inquiry: a front-page exposé, two sidebar articles and a full page of previously unpublished black-and-white photographs describing how the newspapers -- The Herald in the morning and The Leader in the afternoon -- virtually ignored the civil rights movement in Lexington.

Throughout the late 1950's and early 1960's, protesters conducted peaceful weekly sit-ins at the city's racially segregated lunch counters, hotels and theaters. But under orders from their top executives, the newspaper investigation found, both The Herald and The Leader buried coverage of the protests, when they covered them at all. (The two merged in the 1980's, and the paper is now part of the Knight Ridder newspaper chain.)

The poor coverage was not a result of mistakes or oversights, The Herald-Leader concluded, but a conscious strategy by the papers' former managers ''to play down the movement'' in hopes that it would wither away.

''That stance was not unusual among newspapers across the South,'' the article, written by Linda Blackford and Linda Minch, said. ''But from today's perspective, many experts agree that the decisions made at The Herald and The Leader hurt the civil rights movement at the time, irreparably damaged the historical record and caused the newspaper's readers to miss out on one of the most important stories of the 20th century.''

In reaching back four decades, The Herald-Leader went a step further than just about any other Southern paper in trying to set the record straight on its civil rights coverage, historians and journalism experts said.

In the 1990's, The Clarion-Ledger of Jackson, Miss., published articles saying it had slanted coverage and published propaganda at the behest of the Mississippi Sovereignty Commission, which had been created to infiltrate and discredit civil rights groups.

But few newspapers, if any, have taken critical looks at what was the less egregious, but more common, practice of simply disregarding civil rights protests in their hometowns, journalism experts said.

It is unclear whether other newspapers are now considering similar reviews of their civil rights coverage. But several historians and journalism experts said they hoped those papers would follow The Herald-Leader's suit.

''Minimizing the movement was also slanting the coverage,'' said Hodding Carter III, who ran his family's newspaper, The Delta Democrat Times, in Greenville, Miss., in the 1960's, before going to work for the Carter administration.

''A revolution was going on, and ignoring it was pretending it was a few flecks of foam on top of the waves,'' said Mr. Carter, who is now president and chief executive of the John S. and James L. Knight Foundation, which focuses on journalism and communities.

Reaction to the articles has been largely positive. ''I would say better late than never,'' said the Rev. Henry W. Jones, 62, who participated in many of the sit-ins and is now pastor of Mount Zion Second Baptist Church in Atlanta.

But there are also some in Lexington, home of the University of Kentucky, who say that while The Herald-Leader's articles were welcome, they do not think muted coverage of the civil rights movement was wrong. By playing the protests down, they said, the papers may have allowed Lexington to integrate more peacefully than other Southern cities did.

''I didn't think it was the worst strategy,'' said Edward T. Houlihan, a former president of the Lexington Chamber of Commerce who is now executive director of the city's history museum. ''This community got through it a lot better than other communities.''

Audrey Ross Grevious, who led many of the sit-ins, said she was still bitter about its omissions. ''It took me a long time before I would read that paper again,'' Ms. Grevious, 74, said.

Ms. Grevious, a retired teacher, said she started organizing demonstrations after attending a convention of the N.A.A.C.P. in New York City around 1960. On the train ride home, she said, she became furious about segregation for the first time in her life when she was required to move to a rear car after the train crossed the Mason-Dixon line.

''I had lived with segregation all my life,'' she said. ''But the reality really hit me then. I was the same person I had been when that train left New York.''

For several years, she organized weekend sit-ins at lunch counters, movie theaters and hotels. Garbage and feces were dumped on her lawn. A restaurant patron threw a drink on one of her nicer suits, which she has kept as a soiled souvenir. At one lunch counter, the manager swung a chain barrier into her legs for several hours, causing pain that stays with her to this day, she said. But she did not budge.

''We were hoping we would get coverage, so that people would see how segregated things were,'' she said. ''But they only wrote stories when somebody was arrested.''

In fact, the papers published more articles than that, but most were just a few paragraphs long, buried deep inside the paper. Even the Louisville papers, the liberal Courier-Journal and black-owned Defender, covered the Lexington movement in more depth, said Gerald L. Smith, a University of Kentucky historian.

In the course of researching a 2002 book on Lexington's blacks, Mr. Smith said, he was stunned to discover how early Lexington's sit-ins began, in 1959, and how persistent they remained. He and Mr. Houlihan also uncovered a trove of photographs of the demonstrations by a local amateur photographer, Calvert McCann. The Herald and The Leader had never run such photographs, and the images were a revelation to him.

''Usually, historians make a big splash by uncovering things from the 1800's or earlier,'' Mr. Smith said. ''But here, we found something from our lifetime, and we hadn't even known about it.''

Marilyn W. Thompson, The Herald-Leader's new editor, said she planned to run follow-up articles profiling some of the surviving civil rights protesters and scrutinizing the racial attitudes of the late publisher, Fred Wachs, who set the policy on not covering the protests.

For Ms. Thompson, 51, who started work at The Herald-Leader in late June, the July 4 articles were among the first she edited. When Mr. Voskuhl initially proposed the idea, she had just left The Washington Post to take time off to recover from breast cancer treatment and to update her biography of the late Strom Thurmond, the senator and former segregationist from South Carolina.

Ms. Thompson, who broke the story that Mr. Thurmond had fathered a daughter with one of his family's black maids, had just been reading gripping descriptions of the civil rights movement when she received Mr. Voskuhl's message.

''I was excited,'' she said. ''You always hear that cancer does this to you. My attitude was, 'Go for it!'''

Mr. Carroll, who started it all, said he had not seriously considered reviewing the paper's civil rights coverage while he was the editor. In retrospect, he is not sure that was the right decision.

''I think I'd have been a bit uncomfortable attacking the work of our predecessors,'' he said. ''I wish I had done it while I was there.''

Photos: Nietta Dunn at a 1960's sit-in in Lexington, Ky., where the newspapers ignored many protests. (Photo by Courtesy Calvert McCann)(pg. A1); Henry W. Jones led a civil rights protest in Lexington in the 1960's. He said The Herald-Leader's recent articles were ''better late than never.'' (Photo by Courtesy Calvert McCann); The exposé of the strategy by The Herald and The Leader ran July 4. (Photo by Lexington Herald-Leader); Marilyn W. Thompson, the editor, is planning follow-up articles. (Photo by Mark Cornelison/Lexington Herald-Leader for The New York Times)(pg. A17)