If it were a made-for-TV movie, it might be called Invasion of the Advertisers.

With audiences for network television shrinking, and more viewers zapping through commercials on recorded TV, some of the industry's most powerful advertisers are securing roles for their products inside prime-time sitcoms and dramas, once considered off limits for such overt promotions.

"Traditional commercials resonate better when they accompany products placed within a show," says Jeff Bell, vice president of marketing for Chrysler and Jeep at Chrysler Group, a unit of DaimlerChrysler AG.

Forms of product placement have been around almost as long as TV advertising itself, but the practice has been limited largely to sports telecasts, live entertainment and, more recently, reality shows and soap operas -- not the blue-chip scripted shows that are among the most valuable real estate on TV.

But even those shows are no longer sacrosanct, on some networks. In the current season, for example, Ford Motor Co.'s vehicles have been featured on 24, the acclaimed action drama on News Corp.'s Fox. And a shiny, orange Beetle convertible from Volkswagen AG had a big role in the teen superhero drama Smallville on Time Warner's WB network last year.

NBC, the No. 1 network among 18-to-49-year-old viewers (advertisers' most sought-after group), is grappling with how much content territory to cede to marketers. NBC rejected a lucrative deal involving marketers including Ford's Lincoln Mercury and Sony Corp.'s Sony Electronics for its glitzy new drama Las Vegas last year. According to people familiar with the matter, the network was leery of offending traditional advertisers. NBC says it passed on the idea "for creative reasons."

"We continue to explore the value," of product placement in scripted comedies and dramas, says Marianne Gambelli, executive vice president overseeing prime-time ad sales for the network. "How do you make it work? Where does it fit in? Where doesn't it fit in? How do you make it organic?"

CBS and UPN also are charting their way. So far, they haven't directly placed advertisers' brands or logos into prime-time fare. CBS says it remains open to product placement on scripted shows.

The networks aren't the only ones that make such deals. Familiar brands often pop up in prime time not as part of network-advertising deals but as the result of behind-the-scenes maneuverings of so-called product-placement shops. These tiny, discreet outfits maintain close ties with prop masters, set designers and executives at production studios and use their connections to get advertisers' branded products -- from handbags to computers -- in front of the camera on TV's hottest shows.

In June, AIM Productions, a New York product-placement concern, got Unilever PLC's Ragu Express, a packaged pasta-and-sauce meal, an eye-catching role on Everybody Loves Raymond on Viacom's CBS; in the episode, Ray stalked his wife in a supermarket and knocked over an entire display of the product. AIM also got Interbrew SA's Rolling Rock beer a gig on Ed, on General Electric Co.'s NBC in October. Another placement firm, Norm Marshal & Associates, got Microsoft Corp.'s Xbox game machine onto CBS' Two and a Half Men in September. It also helped arrange the ongoing appearances of General Motors Corp.'s Hummer H2 in episodes of CBS' CSI: Miami.

Advertisers themselves -- not their ad agencies -- generally keep product-placement companies on retainers ranging from $20,000 to $100,000 a year, says Patricia Ganguzza, president of AIM Productions, which counts Unilever and Kraft Foods as clients.

Watchdog groups have long decried product placements for blurring the line between content and advertising without adequately informing viewers. And the networks themselves appear to be divided on how far they want to open the gate. "You've got to wonder when it starts to destroy the entertainment value," asks Tom Wolzien, a former television executive who is senior media analyst for investment research firm Sanford C. Bernstein & Co.

In some instances, placements are extremely subtle. For example, Euro RSCG MVBMS Partners, an ad agency owned by Havas SA and working for client Polaroid, handed cameras to the band OutKast, whose hit song Hey Ya includes the lyrics, "Shake it like a Polaroid picture."

According to Ron Berger, the ad firm's chief executive, the cameras have appeared with the band on NBC's Saturday Night Live and the Vibe Awards on Viacom's UPN. "It's like advertising," says Mr. Berger. "If it's done very well, it's great. If it's done badly, it's horrible."

When it comes to reality shows and soap operas, the networks have welcomed product placement. NBC recently agreed with DaimlerChrysler to weave a Chrysler automobile into The Apprentice, a reality show about a competition to become Donald Trump's protege. And Procter & Gamble Co. products are set to appear on CBS' Survivor: All-Stars.

Last year, Avon Products' Mark cosmetics line, aimed at young women, got a prominent role on the NBC soap opera Passions. A young female character became a Mark representative and talked up the brand. CBS, meanwhile, approved a deal weaving Butterball turkeys into storylines on As The World Turns and Guiding Light near Thanksgiving.

WB, Fox and Walt Disney Co.'s ABC say they examine product placements on a case-by-case basis. "There are do's and don'ts, and they are evolving," says Bill Morningstar, executive vice president of media sales at the WB network.

AIM Productions' Ganguzza expects to see more placement deals involving prime-time dramas and comedies. "The brands hold the reins, and the networks realize that marketers have started shifting more dollars into nontraditional media, including product placement, because of its sexy appeal," she says.