Easier to order at home than a pizza, bigger than rock music, it's arguably the most profitable enterprise in cyberspace. AT&T is in the business. Yahoo! and AOL profit from it. Westin and Marriott make more money selling it than they do snacks and drinks in their mini-bars. And at a reported $10 billion a year, it boasts the kind of earnings every American business envies.

It's pornography - and with adult movies, magazines, retail stores, and the growth of the Internet - business is booming.

To begin its fall broadcast season, FRONTLINE presents "American Porn," airing Thursday, October 4, at 9 P.M. on PBS (check local listings). The one-hour documentary examines America's original sin business and some of the well-known top corporations that quietly profit from it.

"The pornography business has always been about seduction," says FRONTLINE producer/director Michael Kirk, " Now, it's seducing big business, which stands to make billions from movies, satellite deals, and the Internet."

In "American Porn," FRONTLINE goes inside some of the most successful pornography businesses to see how their profits have exploded in the past few years: At Larry Flynt's Hustler organization - where "synergy" is the buzzword - publishing co-exists with movies, strip clubs, sex shops, and the Internet to the tune of $400 million; at popular Internet site Danni's Hard Drive, owner Danni Ashe went from exotic dancer to dot-com millionaire virtually overnight, earning $8 million last year alone. While most Americans decry the avalanche of sexually explicit material, the profits speak for themselves. Large numbers of Americans are finding something they like in the adult entertainment arena.

Both Flynt and Ashe credit the 1990s explosion of adult material to the ease of viewing and ordering from the Internet. Equally important, they say, was the Clinton administration's laid-back attitude toward pornography.

"I think the adult entertainment business has experienced a lot of freedom in the last eight years," Ashe says.

Pornography Producer Mark Cromer agrees. "When Clinton came in," he says, "it was definitely blue skies and green lights."

So much so, some former Justice Department officials say, that corporate America felt it was safe to enter the profitable porn market.

"Companies like AT&T bought up a cable company, signed contracts with the Hot Network, which is a hard-core pornographic site," Patrick Trueman tells FRONTLINE. The former head of the Justice Department's Obscenity section in the Reagan and Bush administrations, Trueman now represents the American Family Association, a non-profit organization promoting traditional family values.

"Other mainstream companies thought that 'We can do this, too,' he says. "And why not? There's a big market and no penalty."

Former Justice Department attorney Bruce Taylor concurs. "If there had been continued federal prosecutions [for obscenity], you wouldn't see the Internet presence of the porn syndicate as big as it is today," says Taylor, who has prosecuted more obscenity cases than anyone in U.S. history. "The combination of the industry's willingness to go on the Web in a big way and the prosecutors' not indicting them for it allowed it to explode beyond anybody's imagination."

But times have changed. Clinton is out, Bush is in, and porn moguls are nervous. What's more, these former Justice Department prosecutors are encouraging the Bush administration to launch a new attack on the porn industry - including its silent, white-collar corporate partners. In an attempt to head off an anti-porn government crackdown, the top adult entertainment executives have created a list of twenty one pornography no-no's. Dubbed the "Cambria List" after its drafter, First Amendment attorney and legendary pornographer defense counsel Paul Cambria, the list warns porn producers against showing such acts as sex between a black man and white woman, urination, and facial ejaculation.

The Cambria List has convinced producer Mark Cromer and other producers that the very pioneers of the pornography business are selling out in order to appear mainstream.

"It's a bunch of rich guys running scared," Cromer tells FRONTLINE. "It's a bunch of guys who were, maybe, rebels in the '70s and '80s and don't want to fight anymore. They want to take their chips out of the bank and cash them in and go home and play golf."

But big pornographers aren't the only ones concerned. Big business is also wary.

Until now, companies like AT&T have argued they are like the post office - delivering material people have ordered. They claim they are meeting a popular demand and see nothing illegal or wrong in what they are doing. But such companies may be vulnerable not only to public and legal pressure, but also to the more immediate problem of children getting easy access to adult material through cable and the Internet.

The moral crusaders certainly won't let them off the hook, and what's more, they have a dream scenario: that the government will prosecute and embarrass the companies profiting from pornography.

"I think if you get a mainstream company...into a grand jury where you intend to indict, the wise thing for their lawyers to do is plea bargain the case. You don't want to risk a conviction and your chief people being put in jail. You don't want to risk the shareholders' equity in this company," says former Justice Department official Patrick Trueman. "If you do get a conviction, there will be other mainstream companies that will say, 'Well, what's the percentage in this?'"

"American Porn" is produced and directed by Michael Kirk and co-produced by Jim Gilmore. The correspondent is Peter J. Boyer. The writers are Michael Kirk and Peter J. Boyer.

FRONTLINE is produced by WGBH Boston and is broadcast nationwide on PBS.

Funding for FRONTLINE is provided through the support of PBS viewers. National corporate funding for FRONTLINE is provided by NPR©.

FRONTLINE is closed-captioned for deaf and hard-of-hearing viewers.