In July 2007, Sherk successfully defended his title against Hermes França at UFC 73 .  After the fight, the California State Athletic Commission (CSAC) announced that Sherk had tested positive for Nandrolone , a banned steroid , in a urine test the day prior to the fight. After testing positive for 12 ng/ml of Nandrolone, Sherk was fined $ 2,500 and suspended from competing in California for one year.  Sherk's suspension was reduced to six months after appealing his allegations on December 4, 2007, making him eligible to fight in early January 2008.  Sherk argued that errors were made in lab testing procedures. He asserted that the lab had failed to properly test the vials used in earlier, positive tests for any remaining steroid content, which may have resulted in his sample becoming contaminated.  Quest Diagnostics and the CSAC denied any errors were made.  Following the CSAC's decision to uphold the results of the positive steroid test, the UFC officially stripped Sherk of his Lightweight Championship.  At UFC 80 , . Penn defeated Joe Stevenson to win the vacant title.  After the fight, UFC president Dana White announced that Penn's first title defense would be against Sherk, who was reinstated by UFC in April 2008, and has tested clean ever since.  Sherk and Penn fought at UFC 84 on May 24, 2008. Sherk lost by TKO in the third round after failing to answer the fourth round bell.