On July 11, 2009, heavyweight champion Lesner (4-1) defended his title against Mir in UFC 100. Lesnar won in a second-round stoppage after a series of right hands to Mir's face.

Lesnar ended the night by taunting Mir while he was still on the ground and made hand gestures to the audience, which responded by booking Lesnar.http://www.forbes.com/feeds/ap/2009/07/12/ap6644267.html

In the second round, Lesnar continued the assault, landing blow after blow to Mir's face until it was swollen and bloody and hte match was ended.http://www.8countnews.com/news/125/ARTICLE/1745/2009-07-13.html

With Mir on the ground, Lesnar taunted his opponent and gave the crowd an obscene hand gesture. The crowd responded by booing. Lesnar apologized for his actions the next day.http://www.hispanicbusiness.com/entertainment/2009/7/13/brock_lesnars_apology_to_ufc_and.htm

After the fight began, Lesnar scored an early takedown on Mir. However, Lesnar was penalized for striking Mir in the back of the head, an illegal move. Lesnar again took down Mir, but this time, Mir locked a kneebar hold on Lesnar, forcing him to submit at the 1:30 mark in the first round. Frank Mir was awarded the victory due to Lesnar's tap out.FOX Sports: Reality bites: Mir submits Lesnar at UFC 81 (February 3, 2008)