The Nevada State Athletic Commission (NSAC) today confirmed that 13 of the 22 competitors who were tested for illegal/banned substances after competing at UFC 109: "Relentless" on Feb. 6 have all passed with flying colors.

Main event participants and former UFC heavyweight champions Randy Couture and Mark Coleman as well as Nate Marquart, Chael Sonnen, Paulo Thiago, Demian Maia, Matt Serra, Mac Danzig, Phil Davis, Chris Tuchsherer, Joey Beltran, Melvin Guillard and Rob Emerson were all screened for performance enhancers such as steroids and drugs of abuse like cocaine and marijuana, among others.

Results from these battery of tests all returned negative.

The fighters mentioned above were randomly selected. However, athletic commissions typically test the main event participants and fight night winners, as well as those who have failed drug tests in the past.

UFC 109: "Relentless" featured Randy "The Natural" Couture putting a lopsided beatdown on fellow forty-something Hall-of-Famer Mark "The Hammer" Coleman en route to a second round submission win.

In middleweight action, Chael Sonnen upset Nate "The Great" Marquardt to steal the 185-pound number one contender spot and a chance to challenge the winner of Anderson Silva vs. Vitor Belfort in late 2010.

For complete UFC 109 results and blow-by-blow coverage of the main card action click here and here.