50. Jose Sergio Gabrielli de Azevedo
50. Jose Sergio Gabrielli de Azevedo
CEO, Petrobras

Gabrielli leads an experienced management team that doubled Petrobras's reserves with last year's massive discoveries in "presalt" formations off the Brazilian coast. If these discoveries pan out as expected, the Brazilian state oil company could double its reserves and production volume over the next decade. Gabrielli and his team achieved solid results over the past year, increasing sales by 13% and profits by 30%. However, Brazilian government authorities ultimately call the shots at Petrobras, not Gabrielli. And there's evidence that the government doesn't always run Petrobras for the benefit of its shareholders. Some investors believe that the government manipulated a 2009 share offering to boost its own stake by diluting minority shareholders.

--Reporter associates: Cappy Lyons and Marilyn Adamo

This article is from the December 12, 2011 issue of Fortune.
By Richard McGill Murphy, contributor - Last updated November 17 2011: 5:58 PM ET