The drama began with a tiny ad in a local newspaper -- a notice that asbestos was about to be removed from the management office at Altgeld Gardens, the all-black public housing complex where young Barack Obama worked as a community organizer.

"You think it's in our apartments?" a worried mother asked.

"I don't know," Obama replied. "But we can find out."

What followed, Obama says in a memoir, was a life-altering experience, an early taste of his ability to motivate the powerless and work the levers of government. As the 24-year-old mentor to public housing residents, Obama says he initiated and led efforts that thrust Altgeld's asbestos problem into the headlines, pushing city officials to call hearings and a reluctant housing authority to start a cleanup.

But others tell the story much differently.

They say Obama did not play the singular role in the asbestos episode that he portrays in the best-selling memoir "Dreams From My Father: A Story of Race and Inheritance." Credit for pushing officials to deal with the cancer-causing substance, according to interviews and news accounts from that period, also goes to a well-known preexisting group at Altgeld Gardens and to a local newspaper called the Chicago Reporter. Obama does not mention either one in his book.

"Just because someone writes it doesn't make it true," said longtime Altgeld resident Hazel Johnson, who worked with Obama on the asbestos campaign and had been pushing for a variety of environmental cleanups years before he arrived.

U.S. Rep. Bobby L. Rush (D-Ill.) said it was Johnson's work, as well as asbestos testing conducted by the Chicago Reporter, that sparked the interest of Chicago officials and prompted Rush, who at the time was a City Council member, to launch an inquiry. Though he has not read Obama's memoir, Rush, who has been a political rival of Obama in recent years, said Johnson's role was so prominent that he was "offended" by anyone telling the Altgeld story without including her.

"Was [Obama] involved in stuff? Absolutely," said Robert Ginsburg, an activist who worked in Altgeld with Johnson and Obama. "But there was stuff happening before him, and after him."

No one disputes that Obama was active in organizing Altgeld residents. Several who worked directly with him say he was the most effective organizer they had seen -- a surprise, given his youth. "He was our motivator," said Callie Smith, now 50. "We did all the work, but he was our inspiration."

The varying accounts of what occurred 20 years ago are noteworthy because Obama, now a freshman U.S. senator, has begun a campaign for the White House after three years on the national stage.

Beyond Illinois, where Obama was a state legislator, much of what the public knows about the Chicago Democrat comes from his two best-selling books. On the campaign trail, he has said that through the books he has revealed more of himself to the public than has any other candidate. They provide "insights into how I think and how I feel about the issues facing America," he told reporters this month, according to an account in the Wall Street Journal. Many people at his rallies bring copies.

But "Dreams From My Father," the first of Obama's books, is not a historical account. In it, Obama uses literary techniques that are rarely found in political memoirs.

Dialogue in the memoir is an "approximation of what was actually said or relayed to me," Obama wrote in its introduction. For the sake of compression, he wrote, some characters are "composites of people I've known, and some events appear out of precise chronology." Most names in the book were changed for the sake of privacy, he wrote.

And though most memoirs place their authors at the center of events, critics of "Dreams From My Father" say the book unfairly omits others responsible for the successes of the asbestos campaign, an event that Obama portrays as central to his maturation as a political leader. For example, Johnson is not mentioned, and no character in the book appears to resemble her, even though she was already a prominent Altgeld activist and her presence in the anti-asbestos effort is confirmed by interviews and news accounts at the time.

An Obama spokesman said the memoir was never intended to be a complete account of Altgeld nor to portray Obama as a hero, but merely was the recollections of one activist. Published in 1994 and re-released in 2004, the book primarily tracks Obama's journey to racial identity as the child of a black Kenyan father and a white Kansan mother.

"This is making a mountain out of flat land," said Robert Gibbs, the Obama spokesman, referring to inquiries from The Times. "The book isn't a history of social efforts to help the area. It was about what he was involved in."

Built in the 1940s to house black industrial workers, Altgeld Gardens has long been called a "toxic doughnut." The community is surrounded by a massive landfill, a paint factory, an odor-emitting sewage plant and the polluted Calumet River.

Obama arrived at Altgeld soon after graduating from Columbia University in 1983. He had taken a job with a small group called the Developing Communities Project, which aimed to help people who were struggling after plant closures and other economic troubles.