The purpose of this work was to assess the oxidative dissolution of uranium from a uraninite-containing rock in acid sulfate solutions under test conditions relevant to uranium leach mines and acid mine waters. Uranium dissolution in acidified mineral salts solution was slow and the predominant carbonate mineral (rhodochrosite) in the rock sample continued to consume acid. Bacterial inoculation (Thiobacillus ferrooxidans) and additional Fe2+ or S-0 were tested in efforts to enhance the dissolution. Addition of Fe enhanced the solubilization of uranium, whereas S-addition had little incremental effect on the dissolution with and without bacterial inoculation.