Reduction of TeO32− by SeS2O62− in acidic solution gives a black mixture of Se and Te. Intermediary products are SeSO32−; [O3S−Se−Te−Se−SO3]2− and Selenandi-sulfonates, containing 1–4 Se-atoms in the chain. The anions are separated by high voltage paper electrophoresis and identificated radiochemically, using35S−,75Seaand132Te labelled reactants of detected specific activity. For the formation of the anions the reduction of TeO32− by SeSO32− is discussed.