Two weeks ago, more than 1,000 Dutch fans sat in their underwear to watch a World Cup game. That's because officials wouldn't let them in the stadium wearing orange pants bearing the name of a Dutch brewery, which was not an official sponsor of the soccer championship.

Big events mean big opportunities for what the industry calls guerrilla or ambush marketing, a term that applies to bringing awareness to a brand name without using the usual, approved forms of advertising. Often, as in the case of the Dutch brewery, the efforts do not meet with the approval of event hosts.

When the All-Star Game comes to Pittsburgh, look for the group of college students in purple shorts and bright T-shirts who will be running around town to promote Penn Avenue ad agency Kolbrener Inc.

Outrageous ad stunts, however, are being strongly discouraged, said Brian Bronaugh, president of the Pittsburgh Ad Federation and creative director at Strip District agency Mullen. "Major League Baseball has put a heavy hand on it," he said, sounding frustrated.

Mr. Bronaugh said he understood the need for rules but said he would like more openness to nontraditional tactics, which, he thinks, would add vibrancy to the city. "Having our companies have a cool factor is a good thing."

He heard the creative types at one company were talking about projecting their logo onto one of Pittsburgh's rivers. Another business reportedly was warned off a proposal to do something similar to the blue-painted people Highmark Blue Cross Blue Shield sent out into the community a few years ago without saying who they represented.

Pittsburgh has long had strict rules prohibiting the kind of massive advertising banners that show up in places like New York City. That won't change for the All-Star events, a move that might open the door to future requests, said Jeremy Smith in the city zoning office.

Building owners could have picked up some spare change. After last year's All-Star Game, the Detroit News reported that a huge Chevrolet banner hung from the Detroit Opera House for a month brought the arts organization enough to pay one employee's annual salary.

The Motor City's rules might have been bent a bit in that case. At least one company considered bending them in Pittsburgh this year by draping a big vinyl sign on a building facing PNC Park and asking permission later. The logistics apparently proved too difficult, so it never got that far.

City officials have agreed to allow signs promoting the game or events around it. Any advertising or mention of sponsors is supposed to cover less than one third of the sign.

To see what that looks like, check out the more than 1,000 All-Star banners sponsored by XM Satellite Radio that have been hung along city streets. An illustration designed by Pittsburgh native Burton Morris fills the bulk of the image with the XM logo at the bottom.

Purely congratulatory signs cheering the presence of the All-Star Game also seem to be fine.

There are other ways to get in front of the All-Star crowds, some officially connected with Major League Baseball and some not. Nike has taken out ads on Port Authority buses timed to the event, according to a spokesman for the transit organization. Local businesses are buying cable TV time during All-Star programming.

Kolbrener decided the guerrilla route could be effective without causing trouble, said George Potts, director of business development.

The runners, wearing the message "Run with Kolbrener," will get out once a week through July 19, twice during All-Star week. The students will be paid with gift cards, keeping the cost of the promotion down.

Asked if fans wearing the wrong logos might be tossed from the All-Star Game, like those at the recent World Cup game, John Brody, MLB's senior vice president of corporate sales and marketing, said he was not anticipating any problems, adding, "We hope people wear a lot of black and gold."