In a ceremony at FBI headquarters, Walter Lee Williams and Jose Manuel Garcia Guevara were unveiled as the 500th and 499th persons, respectively, to be added to the infamous roll call, the agency said in a statement.
Williams is wanted for allegedly sexually exploiting children and traveling abroad to have sex with children.
Garcia Guevara is accused of involvement in the 2008 rape and killing of a 26-year-old woman in Louisiana.
Some 469 people on the "Top 10" list have been captured or located. Of that number, 155 were found because of citizen cooperation, the FBI said.