Chromium(VI) was reduced by Thiobacillus ferrooxidans grown with elemental sulphur as the sole energy source. Chromium(VI) reduction (as high as 2000 mu M), was due to the presence of sulphite and thiosulphate, among others with high reducing power which was generated during the sulphur oxidation by the bacteria. Therefore, Thiobacillus ferroxidans could be used to treat chromium(VI)-containing industrial effluents.