LAS VEGAS — As UFC announcer Bruce Buffer likes to say: "And now ... it's time."

After months of hype, Hilo's BJ Penn and Canada's Georges St-Pierre will meet in the main event of UFC 94 today.

Both fighters made the 170-pound weight limit at yesterday's official weigh-in at the MGM Grand Garden Arena. Penn weighed 168; St-Pierre was 170.

The difference could be even greater during the fight, when the 5-foot-9 Penn is expected to add no more than a pound or two, if at all. Meanwhile, St-Pierre said he could add as many as 15 to 17 pounds to his 5-10 frame.

"I'm ready," Penn said after the obligatory staredown with St-Pierre after yesterday's weigh-in. "I got nothing else to say. Let's go."

Both fighters are chasing history, making it one of the most anticipated bouts in the history of the prestigious UFC organization.

St-Pierre, who has a professional record of 17-2, is seeking to become the first fighter to own two victories over Penn. He defeated Penn via split decision in 2006.

Penn is seeking to become the first fighter in UFC history to own two world championships at the same time. He has a professional record of 13-4-1, and is the current UFC lightweight (155 pounds) world champion.

"When this whole fight started, everybody was talking about the legacy thing, but the only way you get that legacy is to win the fight," Penn said. "I got a tough fight ahead of me. If I come out the victor, then we can start talking about legacy."

The winner will also have a legitimate claim in the best pound-for-pound fighter in the world debate.

"Winning two championships would be great, but it's not so much about that as it is about who you beat to get those championships," Penn said. "For me, saying I beat Georges would be a bigger thing because of who he is. Everybody says he's good at everything, this and that, so even if this wasn't for a championship I would consider it my biggest fight."

The matchup has piqued the interest of fans around the world. Around 5,000 showed up for the weigh-in yesterday, and the MGM Grand Garden Arena, with a seating capacity of 17,157, is already sold out for today.

The recent dominance of both fighters only adds to the intrigue

Penn won each of his last three bouts in convincing fashion over three top-ranked lightweights: choke-submission over Jens Pulver, choke-submission over Joe Stevenson, then TKO over Sean Sherk.

St-Pierre has won his last four bouts, all in the welterweight division.

"I know I keep saying this every time we put on an event," UFC president Dana White said. "But I think this is going to be the biggest one we've ever done."

Both fighters epitomize the mixed in mixed martial arts.

Penn has cat-quick punches, and is best known for his world-class jiu-jitsu skills. St-Pierre is adept at overpowering opponents, and is best known for his explosive wrestling takedowns.

Their first meeting was a non-title bout because neither held a championship at the time. Penn won the first round with a flurry of boxing skills. St-Pierre, with his face bloodied after the first round, won the next two rounds with his takedowns.

"Of course I worked on my takedown defense," Penn said. "I'm pretty confident I can defend what ever he tries to bring."

St-Pierre said: "I was not satisfied with that win. I didn't perform the way I wanted to. It's very important for me to show that I can beat BJ Penn, this time with no questions."

Their last fight was scheduled for three 5-minute rounds. Today's bout will be five 5-minute rounds because it is for a world championship.

Because of that, much has been asked about the conditioning of the fighters, especially Penn.

In the first episode of the three-part UFC Primetime series that previewed the bout, Penn was filmed "taking a break" from his training for a few days.

"Like any TV show, they have to make it look like a drama, you know what I mean?" said Rudy Valentino, Penn's head trainer. "BJ is in the best shape he's ever been, believe me."

St-Pierre doesn't believe what he saw on the series.

"I believe this whole thing that he took a vacation ... I believe it is a set up, a fake," he said. "Something to play with my mind. I know he's training really hard like I am."

Really, every angle that can be covered for today's bout has been. All that's left is the actual fight.

"I think it's going to be close," Penn said. "He's good everywhere, I think I'm good everywhere. I just have to grind this thing out and attack him."