Since 16th of July 2004 holders of visas classified in categories E, H, I, L, O and P have to apply for renewal of their visas in their home countries. They will no longer be able to apply for visa re-issuance in the United States. This can be most easily achieved in their home countries, though they have a right to apply at any U.S. Embassy or Consulate General. Foreign temporary workers who do not have travel plans do not need to apply for new visas provided they maintain legal status with the Department of Homeland Security. You can find more information about this change at travel.state.gov website.