With his casual clothes and slightly disheveled hair, Mark Levin doesn't stand out in the scientist-infested Cambridge, MA, neighborhood that's home to his company Millennium Pharmaceuticals. In biotech circles, however, the 51-year-old Millennium CEO and cofounder is known to be somewhat of a character.

First, there's his professional background, which includes not only the typical stints as a drug company biochemical engineer, a manager at Genentech and a venture capitalist, but also forays into brewing and computer sales and marketing. Then there's his uncanny ability to cut lucrative deals for Millennium with big pharmaceutical firms like Bayer and Pfizer, deals that have brought in some $2 billion and that, in some cases, give Millennium 50-50 rights to any drugs developed-arrangements unheard of before Levin hit the scene. And then there are the Halloween parties (Levin reportedly tends to show up in drag) and the CEO's unending fondness for shoes, which he explains this way: "My dad had a bunch of shoe stores, tiny little stores, and so I actually grew up selling shoes. There's nothing I like more than going shoe shopping."