From the UFC site:
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.
Full story:
http://www.ufc.com/index.cfm?fa=news.detail&gid=6848
Damn, Sherk was such a monster (no pun intended)
Apparently both will be suspended 1 year ... so a new champ will obviously need to be crowned. Shame.