This excerpt taken from the PBR 20-F filed Jun 30, 2005.
Preferred shares and the ADSs representing preferred shares generally do not give you voting rights.
A portion of our ADSs represents our preferred shares. Under Brazilian law and our bylaws, holders of preferred shares generally do not have the right to vote in meetings of our stockholders. This means, among other things, that holders of ADSs representing preferred shares are not entitled to vote on important corporate transactions or decisions. See Item 10. Additional InformationMemorandum and Articles of Incorporation of PetrobrasVoting Rights for a discussion of the limited voting rights of our preferred shares.