The fight was B.J. Penn's first title defense of his new lightweight championship belt, against the former champion, Sean Sherk. Sherk had been originally stripped of the belt after testing positive for steroids after his dominant title defense against Hermes Franca. The belt had been put on the line in B.J. Penn vs. Joe Stevenson, and Sherk had been promised the first crack at the new champion. Penn-Sherk was perhaps the most compelling lightweight showdown in years up to that point.
The first round began. The fighters came out strong, not even touching gloves. Sherk went for a takedown which was stuffed by Penn. Penn landed a right. Penn landed another good right, countered with a left by Sherk. Penn landed another right. The crowd began chanting 'BJ'. Sherk landed a hard left. Penn began landing consistent flicking jabs. At this point, Sherk was cut under the right eye. Penn landed a pair of hard jabs. Sherk landed a leg kick. Penn landed a hard uppercut, followed by a jab. The crowd chanted 'B.J.' as the first round ended.
The second round began. Sherk landed a leg kick. They exchanged strikes wildly and Sherk landed another leg kick. Penn landed a good combination, ending with a hard uppercut. They clinched with Penn landing a knee inside. Sherk's eye looked pretty bad now. They broke and Penn landed a hard right. The crowd chanted 'steroids, steroids', apparently aimed towards Sherk. Sherk landed a good combination, countered with a combination by Penn. Penn landed a hard jab. Sherk landed a leg kick and Penn landed a body shot. Penn landed a leg kick. Sherk went for the takedown, stuffed by Penn with fifteen seconds remaining in the second round. The second round came to conclusion.
The third round began and the fighters came out more slowly, not as chipper as they were in the first two rounds. Sherk seemed content once more to keep the fight similar to a kickboxing fight, despite his reputed wrestling skills. They clinched. As they broke, Sherk landed a hard overhand left. Penn went for the takedown and was stuffed, landing a hard left. They exchanged strikes. Sherk landed a hard jab. Penn landed a hard leg kick. Penn landed a good combination. Penn landed a jab. Sherk landed a leg kick. Sherk's face looked horrible. Penn landed a hard jab, trying to end the round well. Penn saw Sherk duck his head and landed a hard flying knee and Sherk went stumbling against the cage and Penn began ground-and-pounding and the fight was stopped at the buzzer. Penn had retained his new lightweight title. Sean Sherk might have broken his hand in the fight.