LAS VEGAS — Floyd Mayweather Jr. is usually content to just win a fight. This time, though, Money Mayweather wanted to earn his cash.

Fighting more aggressively than usual, Mayweather overcame a near knockdown in the second round last night to dominate the rest of the way and win a lopsided 12-round decision over Shane Mosley in their welterweight showdown.

"I wanted to give the fans what they wanted to see, a toe-to-toe battle," Mayweather said. "It wasn't the same style for me but I wanted to be aggressive and I knew I could do it."

Boxing's biggest box office draw remained undefeated in 41 fights, but not before giving his fans and his corner a scare when a right hand to the side of his head buckled his knees a minute into the second, and he had to grab Mosley to avoid going down. Mosley landed another right later in the round, but the rest of the night belonged to Mayweather.

If he didn't please everyone, it was because he couldn't knock out Mosley. But Mayweather won every minute of every round after the second and the normally defensive-minded fighter kept after Mosley until the final bell in a masterful performance that earned him every dollar of his guaranteed $22.5 million payday.

"I think we could have pressed the attack a lot earlier, and then we could have got the knockout," Mayweather said.

Fighting before a star-studded crowd that included Muhammad Ali, Mayweather never came close to dropping Mosley, but landed so many more punches that the outcome wasn't in doubt past the middle rounds. He had an answer for everything Mosley tried to do, landing right hands to the head seemingly at will as the fight progressed.

By the end of the night, Mayweather had put so many rounds in the bank that the only question was whether he would stop Mosley or be content to win a lopsided decision. Mayweather kept moving forward and continued to press the issue in a fight that wasn't in doubt.

Two ringside judges scored it 119-109 for Mayweather, while the third had it 118-110. All had him winning every round past the second.

The Associated Press had Mayweather winning 117-110.

Ringside punch statistics were as one-sided as the scorecards. They showed Mayweather landing 208 of 477 punches to 92 of 452 for Mosley.

Mayweather made Mosley look every bit his 38 years as he landed sharp punches to his head, dominating a fighter who had vowed to turn the bout into the fight of the decade. Mosley tried his best, but couldn't match the speed of the 33-year-old Mayweather, who grew more comfortable with each passing round.

Mayweather was guaranteed $22.5 million but probably will end up with much more once the final pay-per-view buys are added up. Mosley was guaranteed $7 million, and also had a share in the television revenues.

Mosley was a substitute for Manny Pacquiao, who was all but signed to meet Mayweather until a dispute over drug testing derailed the megafight. Instead, Pacquiao beat Joshua Clottey on March 13 in Dallas and is campaigning for a seat in congress in his native Philippines.

"If Manny Pacquiao can take a blood and urine test then we have a fight," Mayweather said. "If not, no fight."

Pacquiao, who watched the fight in the Philippines, told Manilla radio station DZBB that he would agree to blood testing, but only if it is not taken within 24 days of the fight. That is basically the same stance that derailed the fight the first time around.

"For me, as long as the drug test is not done close to the match, I'll agree because if they'll get blood from me close to the match, it will be a disadvantage for me because I'm smaller and he's big," Pacquiao said.