The Nevada State Athletic Commission recently conducted random pre-fight drug tests for illegal/banned substances on four UFC 98 main card fighters.

Former UFC lightweight champ Sean Sherk and his opponent Frankie Edgar along with former UFC welterweight champions Matt Serra and Matt Hughes all passed their drug screenings.

The tests search for performance enhancers such as steroids, as well as recreational drugs like cocaine and marijuana.

UFC 98 takes place on May 23 in Las Vegas, Nevada. The event is headlined by a light-heavyweight title fight between current champ Rashad Evans and number one contender Lyoto Machida. In the evenings co-main event, former UFC welterweight champions Matt Hughes and Matt Serra will look to settle their grudge in a highly anticipated welterweight tilt.

Sean Sherk was previously required to submit a pre-fight drug test before his loss to B.J. Penn at UFC 84 as stipulated by the NSAC following a suspension by the California State Athletic Commission. Sherk previously tested positive for nandrolone after his UFC title defense win over Hermes Franca at UFC 73 in July 2007.