(HOLLYWOOD, CA) -- The Bush administration has very quietly been ramping up efforts to prosecute porn purveyors, starting with a legend of the skin trade, Larry Flynt, and a man who goes by the name of Seymore Butts.

The federal government's renewed interest in attempting to define ``obscenity'' represents a dramatic change from the Clinton years, when the attorney general's office found better things to do with its time than worrying about which graphic sex scenes are obscene and which aren't. This intriguing question occupies the second half of this informative documentary on the porn industry; it even visits the set of a rather disturbing production that makes one wonder how far is too far. The first half of ``American Porn'' is pretty standard stuff: people are making boatloads of money because young girls want to be in the industry, and plenty of people are willing to pay to watch. The show does not examine anything personal or even hint at the motivations of anyone involved in porn.

The digital age has led the porno boom -- business has doubled in the last five years -- and insiders believe that they are doing nothing more than fulfilling public demand. The sex trade had it easy in the 1990s, ``Porn'' posits, because of a presidential administration that saw no need to keep up with the prosecutions of 1980s in which jury after jury was shown porno films and asked: Is this decent? The Justice Dept. won nearly every case it tried.

``If there had been continued federal prosecutions,'' says prosecutor Bruce Taylor, ``you wouldn't see the Internet presence of the porn syndicate as big as it is today. ``

That could change. The attorney general was preparing a major assault on porn, which was curtailed by the events of Sept. 11, and the Supreme Court addressed two porn-related cases in its last session. Flynt, ``Porn'' hints, was and may still be one of the government's targets.

For the most part, the porn industry is being proactively cautious, following a list of taboo subjects drawn up by industry lawyer Paul Cambria. Adam Glasser, who goes by Seymore Butts and specializes in anal sex films, will stand trial this month in Los Angeles; prosecutors believe ``Tampa Tushy Fest,'' a 1999 video, went too far. Glasser was charged with misdemeanor obscenity after a December 2000 raid, and a deputy city attorney says she intends to show the film to a jury to get a ruling on what's acceptable to the community. The documentary does not mention the LAPD (news - web sites) raid of JM Prods. and the charging of Jeff Steward on suspicion of obscenity for the pictures ``American Bukkake 11'' and ``Liquid Gold 5.''

As ``American Porn'' opens, it appears to be picking up where ``Boogie Nights'' left off -- in the land of the quickie video shoot. Clive McClean is shooting an edition of the ``Barely Legal'' video series with two young girls. Cost: $55,000. Profits: $10 million. From there, the documentary heads to Hustler's Sunset Boulevard store and its Wilshire Boulevard headquarters and finally to Danni Ashe, CEO of Danni's Hard Drive, a Web site with live strippers, including herself. Last year Ashe earned $8 million.

The growth industry, we're told, is fetishism. Extreme Associates honchos Lizzie Borden and Rob Black are so set on breaking taboos, such as rape, with startling realism that when the ``Frontline'' film crew visits the set, they end up leaving in disgust. Next they shoot the set of a ``porn boot camp,'' which provides the show's most disturbing sequences; the human cost -- and one really has to wonder about the actors attracted to the Extreme camp -- is not discussed.

Eventually, ``Porn'' makes the tired case that major American corporations such as AT&T and General Motors are pornographers due to their investments in cable and satellite companies that offer pay services with sex programming.

``American Porn'' succeeds at showing the profiteers as regular people. They have standard offices and warehouses; they are men and women of various ages, and they approach all of it from a rather corporate standpoint. They might as well be talking about selling cheese. Producers go the extra mile to put subtitles on Larry Flynt's mumbling and, perhaps most intriguingly, even he is finding the need to be cautious as times are apparently changing.

The cassette reviewed was an explicit version that includes foul language and some distant shots involving nudity. KCET in Los Angeles will air an edited version at 9 Thursday night and the unedited version at 11 p.m. on Sunday.

Filmed in various locations by Frontline and the Kirk Documentary Group. Executive producer, David Fanning; producer, Michael Kirk; co-producer, Jim Gilmore; director, Kirk; writers, Peter Boyer, Kirk.