This excerpt taken from the PBR 20-F filed May 22, 2009.
Holders of our ADSs may encounter difficulties in the exercise of voting rights and preferred shares and the ADSs representing preferred shares generally do not give holders of ADSs voting rights.
Holders of ADSs may encounter difficulties in the exercise of some of their rights as a shareholder if they hold our ADS rather than the underlying shares. For example, if we fail to provide the depositary with voting materials on a timely basis, holders of ADSs may not be able to vote by giving instructions to the depositary on how to vote for them.
In addition, 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.