The disproportionation of aqueous hydrogen peroxide catalyzed by sodium tungstate has been investigated with regard to the multiplicity of the oxygen molecules released. Trapping experiments and detection of the IR luminescence of O-1(2) have shown that the yield of O-1(2) is virtually quantitative. The mono-, di-, and tetraperoxotungstate intermediates W(O-2)(n)O-4-n(2-) (n = 1, 2, 4) have been characterized by UV and W-183 NMR spectroscopies. The diperoxo species is proposed as the precursor of O-1(2).