Ulcerative colitis(UC) is colon localized disease. Broad epithelial cell damage, crypt abscesses and accumulation of neutrophils are recognized for UC. Although the cause of UC is indistinct at this time, there is a growing consensus that abnormal intestinal microflora would be related with UC. There have been several evidences that excessive production of hydrogen sulfide by bacteria in colon would be associated with UC. Sulfate reducing bacteria are able to utilize sulfate as an electron receptor for dissimilation of organic substrate and hydrogen gas, resulting in generating toxic hydrogen sulfide. This review is dealt with the association between sulfate reducing bacteria and UC in aetiology and bacterial pathogenesis.