Autotrophic　denitrification　under　acidic　conditions　using　sulfide　(S2-),　elemental　sulfur　(S-0),　and　thiosulfate　(S2O32-)　as　electron　donors　are　evaluated.　Results　from　batch　and　column　experiments　show　that　when　different　S　species　were　supplied,　different　pH　conditions　and　denitrifier　communities　were　required　for　denitrification　to　occur.　Nitrate　and　nitrite　were　removed　via　autotrophic　denitrification　at　pH　ranging　from　4　to　8,　when　S2-　or　S2O32-　was　the　electron　donor,　while　with　S-0　denitrification　was　only　observed　at　pH　＞　6.　When　S2-　was　used　as　electron　donor,　it　was　converted　to　S-0,　and　S-0　was　not　used　while　S2-　was　available.　When　addition　of　S2-　was　discontinued,　or　S2-　depleted,　S-0　that　had　accumulated　was　used　as　electron　donor　for　denitrification.　These　findings　demonstrate　that　sulfur-based　autotrophic　denitrification　can　proceed　under　acidic　conditions,　but　that　the　addition　of　appropriate　S　species　and　the　presence　of　an　effective　denitrifier　community　are　required.