Advertising is expected to be upbeat in tone and slick in style. But in the past few years, some of the messages emanating from Madison Avenue have turned ornery. And they've been looking a bit ragged. A few seem like they might possibly be subversive. Consider an ad campaign that was created for Amstel Lite beer: The copy, printed in blocky, uneven lines of type, consisted of an angry rant seemingly written by an enemy of the brand, who urged the public to "Avoid Amstel Lite at all costs!" Then there was a recent series of print ads for California Pizza Kitchen, which, like the Amstel ads, adopted a low-budget, homemade look and an angry tone. Complaining (with tongue in cheek of course) about the unusual choices of pizza toppings offered by the chain, the headline blared, "Stop the madness!"

When not playing the role of screaming anarchist, other advertisers have become graffiti artists?targeting their own ads. Brands like Captain Morgan Rum and Reactor Jeans have created ads in which headlines are crossed out and fake mustaches are scribbled on the faces of fashion models. One clothing designer, Moschino, recently started cluttering its own elegantly photographed ads with stickers bearing cryptic messages like "No one is all black. No one is all navigation_elements/white. Therefore no one is all gray."

So what's going on here? Have the top ad agencies been stormed by insurrectionists? On the contrary, ad agency creative executives themselves are wreaking this faux-havoc as part of the industry's latest attempt to co-opt underground culture and cloak itself in the style of the street. It seems that the great blob of advertising?having previously absorbed rock-and-roll, Beat poets, hip-hop gangstas, and indie filmmakers?has just swallowed its latest counter-cultural morsel: the phenomenon known as culture jamming.

The underground movement first bubbled up in the 1980s and gained steam in the early 1990s. Small renegade groups like San Francisco's Billboard Liberation Front (BLF) and New Jersey's Cicada Corps of Artists drew attention by subverting ad's messages (usually on billboards), changing the words in headlines or playfully altering imagery. The jammer groups sometimes had a political agenda (tobacco ads were a favorite target), but in many cases, jamming was a form of creative expression, an opportunity to make ads funnier and more candid than the original versions. When the BLF, for example, took an Apple "Think Different" ad featuring mogul Ted Turner and slyly altered the headline to read "Think Dividends," it began to seem, for just a moment, as if advertising had started telling the truth.

Initially, advertisers viewed culture jammers as their enemies. In a few instances, outdoor-ad companies tried to discourage the practice by prosecuting the billboard guerrillas, but it didn't do much good. Gradually, however, some advertisers stopped fighting the rebels and started imitating them. "Culture jammers have had a big influence on the look and tone of advertising in recent years," says Annie Finnegan, an executive with the Arnold Communications ad agency in Boston. Finnegan, who has studied and lectured on the phenomenon of "guerrilla advertising" (the industry practice of disguising ads or putting them in unexpected places), notes that a number of advertisers have become highly adept at imitating not just the look of anti-advertising but the whole rogue spirit and attitude of it. "A lot of advertisers now have become almost like pranksters," Finnegan says.

Indeed, the agencies are trying all kinds of tricks that one would expect from underground troublemakers, not ad executives. For example, when the New York agency Kirshenbaum Bond & Partners needed to promote a new cocktail, the agency hired attractive actors, planted them in bars, and had them engage in conversations that included frequent mentions of this particular drink. Down in Miami, the ad agency Crispin Porter & Bogusky (CP & B) hired teenagers to play pranks and place crank phone calls targeting tobacco executives; some of the stunts ended up being used for the anti-smoking TV commercials that CP & B produces. Finnegan reports that a Swedish ad agency placed an ad for travel insurance in a wallet that was later glued to the sidewalk of a busy street to capture the attention of passersby. The Los Angeles office of the agency Deutsch recently fooled many people in that city with a series of fake billboards for "topless traffic school" and other nonexistent businesses; when curious or outraged people called the number in the ad, they were connected to the advertiser that sponsored the campaign. If that sounds like a recipe for confusing and possibly alienating potential customers, it just might be.

Finnegan says that guerrilla advertising can backfire because "sometimes people become angry when they discover they've been tricked by an advertiser." But advertisers seem willing to take that risk?to deface their own ads, to engage in pranks, to do whatever's necessary?because there's a sense that anti-advertising is the only way to connect with today's cynical audience. Kirshenbaum Bond co-founder Richard Kirshenbaum argues that consumers have developed a foolproof radar that can spot an ad immediately and tune it out just as quickly; to get "under that radar," Kirshenbaum contends, advertisers must disguise their ads. One way is to make an ad look like a piece of underground communication. The audience figures out pretty quickly that the ranting poster or the street prank is really an ad?but by then, the thinking goes, the advertiser has scored points for having an ironic sense of humor. Mark Crispin Miller, professor of media studies at New York University, says that anti-advertising's primary purpose "is to appeal to the irreverence of the adolescent mind. These ads nudge us in the ribs and share a smirk with us."

Of course, not everybody appreciates the humor?particularly the billboard guerrillas and media pranksters, who now find it difficult to mock advertisers that are already mocking themselves. The rebels jammed the culture?and now the culture has jammed them right back. Pedro Carvajal of the Cicada group finds that some ads from Madison Avenue look so authentically underground that, he says, "When I see some of them I have to admit, it looks like something done by a culture jammer." Jack Napier, one of the cofounders of the BLF, adds: "When I see ads that cross out their own headlines and write in something self-mocking, my first reaction is, they should be paying residuals to the BLF." But Napier has his own way of dealing with this problem: mounting counter-strikes against the co-opters. For example, he once encountered a Plymouth Neon billboard on which the oh-so-clever advertiser had made it appear as if a spray-can vandal had drawn a Mohawk haircut on the car's roof and changed the original headline from "Hi" to "Hip." "First, I was taken aback, and then I was pissed off," says Napier. "And then I thought, 'Shit, I'm not going to let them get away with that.'" Before long, he was up on the board in the wee hours, changing "Hip" to "Hype" and planting the image of a skull on the car's grill.

In effect, the jammers and the agency co-opters are now battling to see who will control the communication of the streets. But it's interesting to note that the two sides in this war really aren't that different from one another. The young agency creative executives that tend to produce anti-advertising ads share the same irreverent attitude and off-the-wall sense of humor as the jammers. And many of them insist their pseudo-attacks on their own ads represent an attempt to modernize advertising by making it more candid and self-aware. Steve Grasse, who runs the Philadelphia agency Gyro, echoes many of the ad business's young turks when he insists, "I hate almost all advertising." (Except his own, naturally.) Grasse tends to produce rough-around-the-edges, highly sarcastic ads that ridicule the phony feel-good imagery of conventional cigarette and beer ads. Asked whether that approach constitutes something of a rip-off of culture jammers, Grasse barks: "Who the hell are the culture jammers? I haven't taken anything from the underground culture. All the stuff I create is original." Finnegan observes that both the underground rebels like Napier and the young ad-agency hipsters like Grasse "are products of the same advertising-drenched culture and have the same sensibilities. They just went in opposite directions."

There's one crucial difference between them: The ad guys have the money?and the upper hand. These days, they usually manage to think of pranks before the pranksters do. For example, the BLF had every reason to expect that Madison Avenue would be shocked when the guerrilla group recently jammed a Levi's billboard campaign by inserting a sticker with the visage of Charles Manson on the ads. Imagine?Manson as ad spokesman! But the fact is, Steve Grasse and Gyro had already crossed that Rubicon a couple of years earlier when the agency featured Manson in advertising for one of its clothing clients?scoring a hit with consumers. "I feel kind of sorry for the culture jammers," concludes Finnegan. "It seems like now, whatever they try to do, advertising has already gotten there."

Warren Berger is author of Advertising Today (Phaidon), scheduled for publication next year.