Chelatococcus daeguensis TAD1 was demonstrated to be an aerobic denitrifier. It can utilize not only nitrate and nitrite but also ammonium at high temperature (about 50 degrees C). The strain had the capability to remove 122.7 and 71.7 mg L-1 NH4+-N by 18 h at 50 and 30 degrees C, respectively. Triplicate heterotrophic nitrification experiments showed that 32.3 % of removed NH4+-N was completely converted to nitrogen gas by 18 h at 50 degrees C. The denitrification genes involved in C. daeguensis TAD1 were identified and sequenced. It was found that the genes responsible for denitrification in TAD1 were napA, nirK, cnorB, and nosZ. Taken together, TAD1 can be an effective candidate for simultaneous nitrification and denitrificaton at high temperature.