The following is from UFC.com:

Sherk and Franca Test Positive, Both Facing Suspension and Fine

LAS VEGAS, July 19 - Today, the California State Athletic Commission released information stating that UFC Lightweight Champion Sean Sherk tested positive for the banned substance Nandrolone Metabolite and that lightweight contender Hermes Franca tested positive for Drostanolone, also a banned substance, in drug tests following their five-round fight on July 7th at UFC 73 in Sacramento, California.

Both of these substances are anabolic agents, and both fighters face a possible fine and suspension by the CSAC.

"Our policy on fighters using steroids, illegal drugs or any banned substance remains the same - you cannot use them,” said UFC President Dana White. “It's not only unhealthy and unsafe, it is against the law. The UFC fully supports the commission's efforts and we will continue to take measures that keep this sport clean and keep the athletes safe."