Here we show that absence of Sep-tRNA:Sec-tRNA synthase (SepSecS) a key enzyme required for the synthesis of the three trypanosomal selenoproteins does not affect growth of bloodstream forms of Trypanosoma brucei. Both life cycle stages of T. brucei are highly sensitive to auranofin, a compound known to target selenoproteins. However, the same sensitivity is observed in the SepSecS double knockout cell lines indicating that the trypanocidal action of auranofin is not connected to selenoproteins. Finally, we show that absence of selenoproteins does not increase sensitivity to H(2)O(2)-induced oxidative stress. Thus in cell culture normal growth of procyclic and bloodstream T. brucei does not depend on selenoproteins.