There's a minor fashion craze catching on in Boston. It's nothing too expensive--just a $20 T-shirt, in fact. But you can't buy them in the store--they're only available at select locations on the sidewalks of Kenmore Square. Flip to the sports page right now. If the Boston Red Sox beat the New York Yankees in Game Five of the American League Championship Series last night, the shirts are still available. If not, well--wait until next year.

These shirts says "Yankees Suck," in bright red letters over the number 21, Roger Clemens' uniform number when he was with the Red Sox, and they are selling by the thousands.

This is a market that someone should have gotten into a long time ago. As one of the guys behind the Yankees Suck empire said yesterday, "There's a lot of Yankee-haters out there." And never more than this weekend, as the Sox and Yanks met at Fenway Park in the postseason for the first time ever. (I'm not even going to attempt to describe the intensity of the rivalry here. If you're curious, wear a Red Sox hat into Yankee Stadium sometime and find out for yourself.)

So who are Yankees Suck? A couple of recent college graduates and Red Sox fans who don't want their names used here. They've all got real jobs, but in their spare time they have made it their mission, as their Web site (www.yankees-suck.com) boasts, to get all of "Red Sox Nation outfitted in this shirt."

They started making shirts at the beginning of this season, but, as one of them explains to me, the inspiration goes back much further. "It's really a lifetime of hating the Yankees," he says.

The shirts aren't licensed by Major League Baseball, and the Red Sox won't sell them because, according to one of the bosses of Yankees Suck, "they won't let us say 'suck' with a major league team." The Yankees haven't signed off either, and one of the shirt vendors says he's "sure the Yankees will be calling us soon."

In the meantime, Yankees Suck has inspired its share of knock-offs. No fewer than half a dozen varieties of the shirt were on display in the bleachers at Fenway over the weekend, from the blunt white-on-red "Yankees Suck" to the effete calligraphy of "Yankees Suck," gold-on-blue.

The ringleaders of the Yankees Suck racket disdain such imitations. "There's some fake Yankee-haters out there," one sneers. "They're imposters. They're out there to make a buck. We're out there to hate the Yankees."