Nike paid $75,000 to place advertisement banners and posters around Back Bay station in advance of the Boston Marathon -- even though adidas is the Marathon's official sneaker sponsor. (Globe Staff Photo / David Ryan)

At the Back Bay MBTA station, Nike has rented all available ad space. By the T's count, that's 82 spaces, including overhead banners and wall placards. The work went up March 15, two weeks before adidas planned to unveil its own ''station domination'' at the Park Street T stop.

Nike's ads slyly allude to the Boston Marathon, an event that Nike has no official ties to.

Boston Athletic Association, the Marathon's organizer, expressed disappointment but not surprise at Nike's actions. Nike has a reputation for guerrilla marketing, said BAA executive director Guy L. Morse.

In these parts, Nike's marketing around the Marathon has almost become as much a rite of spring as high hopes for the Red Sox. A year ago, Nike said it took out ads on 300 taxi tops; two years ago, it blanketed Park Street station with ads.

Said Morse, ''In my opinion, it can be disappointing and offensive when someone takes advantage of the Boston Marathon without paying for the privilege.''

Around April 1, adidas plans to start its own Marathon marketing efforts, which include ads at Park Street station, wrapping T trolleys in adidas messaging, and billboard ads.

MBTA spokesman Joe Pesaturo said that Nike paid the company that sells the T's ad space $75,000 for its monthlong station-domination program at Back Bay and that adidas will pay $100,000 to make Park Street a shrine for its brand, an amount that adidas disputed.

When it came to T stops, ''we had first choice,'' said Chris Jenks, director of brand marketing at adidas America.

Asked about Nike, he said, ''We can't control what other people do.''

Jenks said adidas won't disclose the specific content of its Marathon ads until their unveiling.

Adidas is well known for soccer. In its ongoing marketing efforts, adidas looks to alert US consumers that its ''innovative'' technologies and designs are equally applicable to its basketball and running shoes, Jenks said.

As for the Nike ads in Back Bay, the Nike name is never mentioned, and its swoosh logo is shown about 10 times.

There are references to April 15, the date of the race, but not the Boston Marathon.

Ads are mostly photos of runners, and they're captioned with the thoughts that might go through the runner's mind during a race. Among the captions: ''Pray for a tailwind.'' ''If it goes bad, I'll call it a workout.''

The campaign is as much about establishing a bond with serious runners as it is about gaining more brand exposure, said Jim Jennings, a Nike marketing manager.

''This is our way of getting Boston excited about the race and letting them know Nike is excited about the race,'' he said. ''Our objective is to be there for the runners. It's to inspire them and support them. And it's also about learning from them.''

Two ads in the campaign might give a bluenose a bad case of the vapors.

In one, the caption of a woman runner in obvious discomfort is, ''Where can I pee?'' A caption under a male runner is, ''Bloody nipples are a trophy.''

To date, the Massachusetts Bay Transportation Authority has received no complaints about the ads. Given the full context of the campaign, it was deemed that they were not inappropriate, Pesaturo said.

Chris Reidy can be reached at reidy@globe.com.