TORONTO -- Brazilian light-heavyweight Thiago Silva tested positive for marijuana following his recent UFC win over Stanislav Nedkov in Macau.
"Silva has admitted to taking the banned substance and has agreed to participate in an approved drug-rehabilitation program and serve a six-month suspension retroactive to the Nov. 10 event," the UFC said in a statement.
The fight was declared a no contest.
Silva will have to pass a drug test when the ban is up before receiving clearance to fight again.
Silva (14-3 with three no contests) defeated Bulgaria's Nedkov by arm-triangle choke in the third round.
It's a second strike against Silva, a former light-heavyweight contender who admitted to doping and tampering with his urine at a UFC 125 drug test.
He said he did it because he injured his back in advance of the January 2011 fight against Brandon (The Truth) Vera.
Silva won the fight, which was turned into a no contest after the failed drug test. The Nevada State Athletic Commission had alleged he submitted a specimen that was "inconsistent with human urine" before the bout.
Silva said, in order to fight Vera, he took injections containing a prohibited substance and then tried to mask the presence of these substances in his urine.
He was banned for a year and fined US$33,750
Vera, after suffering his third straight defeat, was cut by the UFC in the wake of the Silva loss. But he was subsequently reinstated.