In this study, hydrogen sulfide (H2S), ammonia (NH3), and benzene, which represent the major odor from a natural leather process plant, were removed using a fluidized bed bioreactor and biofilter including Thiobacillus sp. IW and a MY microbial consortium. The critical removal rate was 12 g m(-3) h(-1) for (HS)-S-2 I I I g m(-3) h(-1) for NH3, and 28 g m(-3) h(-1) for benzene by the fluidized bed bioreactor, and 8.5 g m(-3) h(-1) for H2S, 7 g m(-3) h(-1) for NH3, and 25 g m(-3) h(-1) for benzene in the biofilter. The average removal efficiency of H2S, NH3, and benzene by continuous operation for over 30 days with the fluidized bed bioreactor was 95+/-3%, 99+/-1%, and 98+/-5%, respectively, whereas that with the biofilter was 96+/-4%, 95+/-4%, and 97+/-3%, respectively. Therefore, the critical removal rate of H2S, NH3, and benzene was higher in the fluidized bed bioreactor, whereas the removal efficiency on the continuous operation was similar in both bioreactors.