Anything associated with the words "a first in UFC history" should be considered significant in the sport of mixed martial arts.

That Hilo's BJ Penn and Canada's Georges St-Pierre are in Honolulu this week to promote their world championship bout Jan. 31 says much about its magnitude.

"After I win this fight, it would be the crowning achievement of my career," Penn said. "There's no one else. I could beat any other name and who cares? This is the one I want, the one everybody wants."

Penn, St-Pierre and UFC president Dana White are scheduled to appear at a press conference/public rally today at the Blaisdell Concert Hall.

The event was originally scheduled for the Waikiki Shell, but was moved to the Blaisdell Concert Hall because of the threat of rain. Doors will open at 4 p.m., with musical entertainment by J-Boogs and Fiji at 5 p.m., and then the press conference around 6:15.

The first 2,000 fans will receive a free UFC T-shirt.

It is the last stop in a three-city promotional tour. Penn and St-Pierre also held press conferences in Las Vegas (site of the Jan. 31 bout) and Toronto (to accommodate St-Pierre's fans).

"This is the first time we've ever done this," UFC president White said. "That's how big this is. But it's also because Hawai'i and Canada are two huge markets for us. And of course, BJ and Georges are two of the best in the world."

Penn is the UFC's lightweight (155 pounds) world champion; St-Pierre is the UFC's welterweight (170 pounds) world champ.

Only St-Pierre's title will be on the line Jan. 31 since the bout will be at 170 pounds. Penn is attempting to become the first competitor in UFC history to hold two world titles at the same time.

St-Pierre is attempting to become the first fighter to beat Penn twice. St-Pierre received a split-decision victory over Penn in March 2006.

"Last time, it was a split decision," St-Pierre said. "This time it has to be clear. That's why we do it again. I call it unfinished business."

Penn, 29, has a professional record of 13-4-1; St-Pierre, 27, is 17-2.

Today's rally may be a rare chance for Hawai'i fans to see such UFC stars in person here.

White said a new state law scheduled to take effect in July 2009 will make it virtually impossible for the UFC to stage an event here.

"It's not happening, period," White said. "The problem is they raised the taxes too high if you want to do an event in Hawai'i. It would crush us (financially)."

The law was designed to help regulate the sport, but White said the promoters of MMA events will be charged "at least 10 percent more" to hold cards in Hawai'i than they would at other places around the world.

"We'd love to do an event in Hawai'i," White said. "But unless they change that tax structure, there's no way."