How true is that memoir?

As he wrote a memoir about being an abused child and adult criminal, Joe Loya didn't feel the need to embellish anything, he says. In fact, he felt the urge to do the exact opposite.

"There were things that I thought there was no way people would believe," Mr. Loya says.

He ultimately left out some of the more outrageous facts about the 673-pound inmate who gave Loya's acclaimed 2004 memoir the title: "The Man Who Outgrew His Prison Cell: Confessions of a Bank Robber."

When it comes to such detail, "it's enough to tell a little bit," he says. "We can't write every story that ever occurred in our lives."

Indeed, no one wants to read an 8,000-page memoir that pores over each waking moment. But now, the controversy surrounding James Frey's bestselling memoir, "A Million Little Pieces," is raising questions about how factual even the most carefully written memoirs are.

"The memoir is a strange kind of performance. It's halfway between fiction and testimony," says Brian McHale, a professor at Ohio State University who studies literary hoaxes. "Anybody in his right mind knows that a memoir is unreliable."

Some memoirs contain more embellishment or fiction than others, however. Last week, TheSmokingGun.com uncovered a number of seeming untruths and exaggerations in "A Million Little Pieces," Mr. Frey's 2003 memoir about his struggle with drug and alcohol addiction. Among other discrepancies, Frey apparently spent just a few hours in jail - not three months, as he writes in the book. (Random House will provide refunds to disgruntled readers, as is their standard practice.)

Frey and Oprah Winfrey, who promoted the memoir last year through her book club, defended "A Million Little Pieces" and said the redemptive power of the book remains unscathed.

Others in the literary world have expressed outrage, including Mary Karr, whose memoir about her dysfunctional family, "The Liar's Club," has spawned many imitators. "My experience is there's no way you can manufacture events and find the truth," Ms. Karr says. "Great memoirs don't take bizarre experiences and make them more bizarre and outrageous. They take bizarre experiences and make them familiar. That's the power."

But some find that power through the techniques of fiction. Indeed, like novelists, many memoirists write pages of dialogue, even if the actual conversations took place decades earlier. They often create composite characters, collapse time, and fill scenes from long ago with lush detail.

"You're taking the highlights of your life. It's a work of art, it's selective, it's subject to memory," says memoirist Lili Wright, author of "Learning to Float" (2000). "A memoir is art, it's literature. It's not journalism, it's not a documentary."

For many memoirists, balancing reality with the art of writing is difficult.

"Every second of the process, you're confronting questions about ethics and the boundaries of what's true and not true," says Nancy McCabe, author of 2003's "After the Flashlight Man."

Some authors consult their journals and diaries. Others, like Ms. Karr, check with people featured in their memoirs and ask them to sign releases stating the books are accurate. This is a good idea, Karr says, not least because "most of the people in my family are armed."

In the larger picture, Karr says such consultations help keep her honest. "For me, the greatest pressure is to tell the truth to the best of my ability, knowing that it will be corrupt, and I'll forget things, and I'm self-serving."

In addition to fact-checking, some memoirists warn readers about the pitfalls of memory.

In his groundbreaking memoir "This Boy's Life," author Tobias Wolff notes that he and his mother disagree over the attractiveness of a dog in the book. He allows some disputed details to stand "because this is a book of memory, and memory has its own story to tell."

It's important to be clear and upfront with readers, says Patricia O'Toole, author of the 2005 biography "When Trumpets Call: Theodore Roosevelt After the White House." "You have to let the reader know what your game is. If you're telling the reader it's the way it really happened, it ought to be the way it really happened."

Frey offers no disclaimer in "A Million Little Pieces," and there's no indication that his publishers wanted one. In fact, publishers have traditionally been more concerned about libel than accuracy in memoirs, says Charlotte Abbott, senior editor at Publishers Weekly. "They don't undergo the same scrutiny as a history or current-events books," she says.

Frey could have sold his book as a novel, and some reports suggest that he tried to do that at first. But nonfiction, Ms. Abbott says, tends to sell better.

Author Ms. Wright hopes people won't lose faith in memoirs. "The reader's with you until proven otherwise, until that trust is broken," she says. "With good reason, readers should trust memoir writers. Most people are doing it the right way."

1977: "The Education of Little Tree" tells the supposedly autobiographical story of a half-Cherokee boy. The book becomes a smash hit in the young-adult market, but the author's real name is exposed, along with the fact that the memoir is fiction.

1983: A German magazine publishes excerpts from what are said to be the diaries of Adolf Hitler. The diaries turn out to be fake.

1993: Anthony Godby Johnson, allegedly a teenage boy suffering from AIDS, writes a wrenching memoir called "A Rock and a Hard Place" to popular and critical acclaim, but journalists are unable to confirm his existence.

1994: A memoir called "My Own Sweet Time" appears in Australia, supposedly written by an aboriginal woman who was raised by whites. The author was actually a white man.

1995: The critically acclaimed "Fragments: Memories of a Wartime Childhood 1939-1948" appears, tracing the author's life as a Polish and Jewish child during the Holocaust. But journalists unmask the author as an imposter reportedly born in 1941.