Madalyn Murray O'Hair never petitioned the Federal Communications Commission to get religious broadcasting off the air. James Dobson never launched a petition drive to stop her.

O'Hair died more than a decade ago, but the rumor about her FCC petition lives on. The commission has received millions of inquiries about it, many the result of church-sponsored letter-writing campaigns. It's gotten so bad that the FCC's official Web site has a page debunking the rumor. (The page notes that in 1974, two other people petitioned the FCC to look into the practices of stations licensed to religious groups. But O'Hair, the famous atheist, had nothing to do with that petition, and it didn't seek a ban on religious programming.)

"It's the mother of all urban legends," said Rich Buhler, founder of TruthOrFiction.com, a site that exposes false "e-rumors." The story resurfaces from time to time; one recent version blamed the supposed O'Hair petition for forcing "Touched by an Angel" off the air.

The FCC story is one of dozens of urban legends with religious themes circulating on the Internet. Snopes.com, the self-styled "urban legends reference pages," lists 49 religion tales.

Most are pure hokum (Scientists drilling in Siberia punch through to hell). Some have a partial basis in fact (Seventh-graders in California are subjected to an intense three-week course in Islam and forced to pray to Allah). Some are comical (St. Chad is the patron saint of disputed elections). And a few are true (Gov. George W. Bush signed a proclamation declaring June 10, 2000, to be Jesus Day in Texas).

Many of the legends seem to appeal to conservative and evangelical Christians and are widely circulated by e-mail and on blogs they read.

But some within the evangelical community have taken on myth-busting as a ministry. Web sites such as TruthMiners.com and Answers.org expose hoaxes and urge Christians not to pass on unsubstantiated rumors.

Christian radio personalities, including Dobson, have pointedly debunked popular e-rumors. They see discussion of urban legends as a tool for teaching about truth, falsehood and Christian integrity.

Writing about the Madalyn O'Hair rumor, for example, the author of one entry on a Christian site said: "Christian credibility has suffered a major blow on this one, folks. May we wise up for His Name's sake!"