A few years ago, footwear giant Nike leased a two-story parking garage in a dilapidated corner of downtown Atlanta. Three years and $3 million later, the garage has blossomed into a splashy Nike store that just happens to be situated next to the prestigious Olympic sponsor village.

Organizers of the Atlanta Olympics say non-sponsor Nike, with its building's unmistakable, 30-foot swoosh, is one of a growing number of companies that insinuate -- in a perfectly legal way -- they are a sponsor of the Games. And it irks them.

"Nike has chosen to put a shoe store at the back door of the sponsor village, standing at the edge of the group picture and trying to look very sponsorlike," said Darby Coker, director of communications for the marketing arm of the Atlanta Committee for the Olympic Games.

"We are not trying to kid anybody into thinking we are a sponsor," Nike spokesman Keith Peters said. "I hear it all the time, and we feel we have every right to be a participant at sports events. We have been with our athletes and track and field longer than the people in Atlanta will have anything to do with sponsors."

The Games don't start until Friday, but the advertising wars have been underway for months. Olympic sponsors each pay $40 million for the privilege of being the exclusive endorser in a given category, such as fast food. No wonder big sponsors such as Coca-Cola, AT&T, Bausch & Lomb, United Parcel Service and McDonald's react quickly when they sense the slightest incursion by "ambushers."

In the strictest sense, "ambushers" are companies that infringe on trademarks and sell counterfeit merchandise. But the term is used broadly in marketing to refer to companies that compete -- without official sanction -- against a rival who has shelled out big bucks to be a sponsor. The Nike building -- on the fringe of the Olympic Park and Olympic Ring in downtown Atlanta -- is one example.

"We've seen the huge Nike area near the park, and if you think about this being the number one event on the planet for the next month, this is the place to do an ambush," said Peter de Tagyos, director of corporate sponsorships and Olympics for AT&T, one of the official sponsors.

Ambushers can't legally use the Olympic rings or words such as "Olympics" or "the Games" in their advertising. And they can't make references to Atlanta or 1996, but that leaves a gray area for some companies and governments.

"It cheapens the atmosphere and cheapens the Games, but this is a free country and they have a First Amendment right to advertise," said Jim Brown, director of Olympic operations for Xerox.

Even the city of Atlanta has been criticized. International Olympic Committee Vice President Richard Pound said today the city ambushed the host committee (ACOG) with its promotional campaign. "It never occurred to us that a host city would set out to ambush its own organizing committee," Pound said.

Companies such as McDonald's, Visa and AT&T have been stung by ambushes in recent Olympics. Marketing experts say a Wendy's television campaign built around the Lillehammer Winter Games of 1994 and figure skater Kristi Yamaguchi is a textbook case of ambushing that left many people thinking non-sponsor Wendy's was the official fast food of the Games.

Television is the most effective means for ambushing because it reaches hundreds of millions of consumers in a flash. Nike's current TV ads -- which have been well received -- feature Michael Johnson and other top Nike-sponsored Olympians. The company can do this without being an Olympic sponsor, as long as it does not use the Olympic rings or mention the Olympics in its ads.

McDonald's and Coca-Cola didn't take any chances on getting ambushed on television. Each company bought all of the commercials in its category for NBC's Olympic telecast. The price for Coke: $62 million.

But observers say AT&T made a critical mistake by purchasing only one-half of its category. Rival MCI swooped in and bought up most of the rest, opening up the possibility for a classic ambush -- to the regret of AT&T.

Fuji and German automaker Audi, and even the state of Florida, all have been slapped by Olympic organizers for linking themselves with the Games. Fuji must remove its logo from at least 12 billboards around the country because they feature U.S. decathlete Dan O'Brien. It's against United States Olympic Committee rules to include an athlete in an ad campaign during the 17 days of the Olympics, unless the athlete receives an exception. O'Brien did not get such an exception, but Johnson did.

A few months back, Audi was asked to remove references such as "best seat for the Games" and "Germany sends its best to Atlanta" from its billboards, according to Atlanta organizers. Florida used Olympic trademarks without permission in its tourism ads. ACOG has a law firm that asks so-called violators to stop whatever they're doing if the committee believes they're breaking the rules.

John Krimsky, the USOC's deputy secretary general, said he expects several big ambushes after the Games begin Friday. One source may be light shows beamed on to the side of Atlanta's skyscrapers, reproducing giant company logos for the thousands milling about in the Olympic Ring.

ACOG has assembled an "ambush police force" of 200 to scout Atlanta and other major cities for last-minute ambushing and counterfeit merchandise. Reports will be filed twice a day from 126 U.S. cities.

The big sponsors such as Eastman Kodak have so much riding on the Games -- increased profits and goodwill -- that they have organized counterintelligence personnel who are fanning out across city streets to look for places where someone could put a sign on a wall or mount a retail stand on a corner.

"We try to think like them and plug all those stops," said Richard Diggelmann, regional director for Olympic programs for Kodak. The film giant, based in Rochester, N.Y., is spending nearly $200 million to stem a slow film processing market-share slide that has dropped several points in the past 10 years, according to a spokesman. Case in point: when a jazzy, six-story electronic billboard in Atlanta became available, Diggelmann bought it to block Japan-based Fuji. He also made sure that 300 retail centers at the Olympic competition sites carry Kodak film.

Another non-sponsor with a huge presence is Korean electronics-maker Samsung. Samsung has several billboards throughout the city with the slogan, "The World Inspires Us." The company also is running a promotional park called '96 Expo that spectators won't be able to miss on their way to some of the competition sites. It's no accident that the Samsung promotion is right under the nose of two Olympic sponsors who happen to be Samsung rivals: Motorola and Panasonic.

"This is permitted under the First Amendment," Coker said, "but we hope the public won't be confused about who is sponsoring the Games."

"We have no intention of ambush marketing at all," Samsung spokesman Clara Kim said. "We are augmenting an international celebration of people coming together. '96 Expo is a free event that gives people who can't get in the Games a place to go."

Not to be outdone, Panasonic has its own thundering ads that prominently make use of the Olympic rings: "Part of the Team," says one Panasonic billboard.

If the best defense is a good offense, nobody has stomped out the ambush threat like Atlanta native Coca-Cola. In addition to buying its television category, Coke has put about 5,000 vending machines and portable spray coolers on city streets. About 50 kiosks have been placed on street corners. And Coke has built its own theme park in downtown Atlanta, called Olympic City, with its huge, red presence. Its marketing of the nationwide torch relay also has been aggressive. "A sponsor can execute the sponsorship in an effective and creative enough way to make {ambushing} difficult," said Mark Preisinger, Coke's manager of media relations. "We execute a strategy very aggressively." CAPTION: Nike, which is not a sponsor of the Olympics, nonetheless has made quite a presence for itself with a complex and 30-foot logo in the heart of activity.