According to the Nevada Athletic Commission, all 12 fighters tested in the UFC-81 anti-doping test on February 2 presented negative results.
Athletes are tested for banned substances such as anabolic steroids and illicit drugs such as marijuana and cocaine.
Check out the athletes tested:
Tim sylvia
Antonio Nogueira
Brock Lesnar
Frank mir
Nathan Marquardt
Jeremy Horn
Rob emerson
Tim Boetch
Tyson griffin
Marvin Eastman
Ricardo Almeida
Chris Lytle